Signal generating method and signal generating device

ABSTRACT

A transmission method for transmitting a first modulated signal and a second modulated signal in the same frequency at the same time. Each signal has been modulated according to a different modulation scheme. The transmission method applies precoding on both signals using a fixed precoding matrix, applies different power change to each signal, and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on applications No. 2011-093540 filed in Japanon Apr. 19, 2011 and No. 2011-140749 filed in Japan on Jun. 24, 2011 thecontents of which are hereby incorporated by reference.

The present invention relates to a signal generating method and a signalgenerating device for communication using multiple antennas.

BACKGROUND ART

A MIMO (Multiple-Input, Multiple-Output) system is an example of aconventional communication system using multiple antennas. Inmulti-antenna communication, of which the MIMO system is typical,multiple transmission signals are each modulated, and each modulatedsignal is simultaneously transmitted from a different antenna in orderto increase the transmission speed of the data.

FIG. 23 illustrates a sample configuration of a transmission andreception device having two transmit antennas and two receive antennas,and using two transmit modulated signals (transmit streams). In thetransmission device, encoded data are interleaved, the interleaved dataare modulated, and frequency conversion and the like are performed togenerate transmission signals, which are then transmitted from antennas.In this case, the scheme for simultaneously transmitting differentmodulated signals from different transmit antennas at the same time andon a common frequency is a spatial multiplexing MIMO system.

In this context, Patent Literature 1 suggests using a transmissiondevice provided with a different interleaving pattern for each transmitantenna. That is, the transmission device from FIG. 23 should use twodistinct interleaving patterns performed by two interleavers (πa andπb). As for the reception device, Non-Patent Literature 1 and Non-PatentLiterature 2 describe improving reception quality by iteratively usingsoft values for the detection method (by the MIMO detector of FIG. 23).

As it happens, models of actual propagation environments in wirelesscommunications include NLOS (Non Line-Of-Sight), typified by a Rayleighfading environment, and LOS (Line-Of-Sight), typified by a Rician fadingenvironment. When the transmission device transmits a single modulatedsignal, and the reception device performs maximal ratio combination onthe signals received by a plurality of antennas and then demodulates anddecodes the resulting signals, excellent reception quality can beachieved in a LOS environment, in particular in an environment where theRician factor is large. The Rician factor represents the received powerof direct waves relative to the received power of scattered waves.However, depending on the transmission system (e.g., a spatialmultiplexing MIMO system), a problem occurs in that the receptionquality deteriorates as the Rician factor increases (see Non-PatentLiterature 3).

FIGS. 24A and 24B illustrate an example of simulation results of the BER(Bit Error Rate) characteristics (vertical axis: BER, horizontal axis:SNR (signal-to-noise ratio) for data encoded with LDPC (low-densityparity-check) codes and transmitted over a 2×2 (two transmit antennas,two receive antennas) spatial multiplexing MIMO system in a Rayleighfading environment and in a Rician fading environment with Ricianfactors of K=3, 10, and 16 dB. FIG. 24A gives the Max-Logapproximation-based log-likelihood ratio (i.e., Max-log APP, where APPis the a posteriori probability) BER characteristics without iterativedetection (see Non-Patent Literature 1 and Non-Patent Literature 2),while FIG. 24B gives the Max-log APP BER characteristic with iterativedetection (see Non-Patent Literature 1 and Non-Patent Literature 2)(number of iterations: five). FIGS. 24A and 24B clearly indicate that,regardless of whether or not iterative detection is performed, receptionquality degrades in the spatial multiplexing MIMO system as the Ricianfactor increases. Thus, the problem of reception quality degradationupon stabilization of the propagation environment in the spatialmultiplexing MIMO system, which does not occur in a conventionalsingle-modulation signal system, is unique to the spatial multiplexingMIMO system.

Broadcast or multicast communication is a service applied to variouspropagation environments. The radio wave propagation environment betweenthe broadcaster and the receivers belonging to the users is often a LOSenvironment. When using a spatial multiplexing MIMO system having theabove problem for broadcast or multicast communication, a situation mayoccur in which the received electric field strength is high at thereception device, but in which degradation in reception quality makesservice reception impossible. In other words, in order to use a spatialmultiplexing MIMO system in broadcast or multicast communication in boththe NLOS environment and the LOS environment, a MIMO system that offersa certain degree of reception quality is desirable.

Non-Patent Literature 8 describes a method of selecting a codebook usedin precoding (i.e. a precoding matrix, also referred to as a precodingweight matrix) based on feedback information from a communication party.However, Non-Patent Literature 8 does not at all disclose a method forprecoding in an environment in which feedback information cannot beacquired from the other party, such as in the above broadcast ormulticast communication.

On the other hand, Non-Patent Literature 4 discloses a method forswitching the precoding matrix over time. This method is applicable whenno feedback information is available. Non-Patent Literature 4 disclosesusing a unitary matrix as the precoding matrix, and switching theunitary matrix at random, but does not at all disclose a methodapplicable to degradation of reception quality in the above-describedLOS environment. Non-Patent Literature 4 simply recites hopping betweenprecoding matrices at random. Obviously, Non-Patent Literature 4 makesno mention whatsoever of a precoding method, or a structure of aprecoding matrix, for remedying degradation of reception quality in aLOS environment.

CITATION LIST Patent Literature Patent Literature 1

International Patent Application Publication No. WO2005/050885

Non-Patent Literature Non-Patent Literature 1

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Non-Patent Literature 2

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Non-Patent Literature 3

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Non-Patent Literature 4

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Non-Patent Literature 11

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Non-Patent Literature 12

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Non-Patent Literature 13

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Non-Patent Literature 14

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Non-Patent Literature 16

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SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a MIMO system thatimproves reception quality in a LOS environment.

Solution to Problem

The present invention provides a signal generation method forgenerating, from a plurality of baseband signals, a plurality of signalsfor transmission on a common frequency band and at a common time,comprising: performing a change of phase on each of a first basebandsignal s1 generated from a first set of bits according to a firstmodulation scheme and a second baseband signal s2 generated from asecond set of bits according to a second modulation scheme, thusgenerating a first post-phase-change baseband signal s1′ and a secondpost-phase-change baseband signal s2′; multiplying the firstpost-phase-change baseband signal s1′ by u and multiplying the secondpost-phase-change baseband signal s2′ by v, where u and v denote realnumbers different from each other; and applying weighting according to apredetermined matrix F to the first post-phase-change baseband signals1′×u and to the second post-phase-change baseband signal s2′×v, thusgenerating the plurality of signals for transmission on the commonfrequency band and at the common time as a first weighted signal z1 anda second weighted signal z2, wherein the first weighted signal z1 andthe second weighted signal z2 satisfy the relation: (z1,z2)^(T)=F(u×s1′, v×s2′)^(T), and the first modulation scheme isdifferent from the second modulation scheme.

The present invention also provides a signal generation apparatus forgenerating, from a plurality of baseband signals, a plurality of signalsfor transmission on a common frequency band and at a common time,comprising: a phase changer performing a change of phase on each of afirst baseband signal s1 generated from a first set of bits according toa first modulation scheme and a second baseband signal s2 generated froma second set of bits according to a second modulation scheme, thusgenerating a first post-phase-change baseband signal s1′ and a secondpost-phase-change baseband signal s2′; a power changer multiplying thefirst post-phase-change baseband signal s1′ by u and multiplying thesecond post-phase-change baseband signal s2′ by v, where u and v denotereal numbers different from each other; and a weighting unit applyingweighting according to a predetermined matrix F to the firstpost-phase-change baseband signal s1′×u and to the secondpost-phase-change baseband signal s2′×v, thus generating the pluralityof signals for transmission on the common frequency band and at thecommon time as a first weighted signal z1 and a second weighted signalz2, wherein the first weighted signal z1 and the second weighted signalz2 satisfy the relation: (z1, z2)^(T)=F(u×s1′, v×s2′)^(T), and the firstmodulation scheme is different from the second modulation scheme.

Advantageous Effects of Invention

According to the above structure, the present invention provides asignal generation method and a signal generation apparatus that remedydegradation of reception quality in a LOS environment, thereby providinghigh-quality service to LOS users during broadcast or multicastcommunication.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a transmission and reception device ina spatial multiplexing MIMO system.

FIG. 2 illustrates a sample frame configuration.

FIG. 3 illustrates an example of a transmission device applying a phasechanging method.

FIG. 4 illustrates another example of a transmission device applying aphase changing method.

FIG. 5 illustrates another sample frame configuration.

FIG. 6 illustrates another sample phase changing method.

FIG. 7 illustrates a sample configuration of a reception device.

FIG. 8 illustrates a sample configuration of a signal processor in thereception device.

FIG. 9 illustrates another sample configuration of a signal processor inthe reception device.

FIG. 10 illustrates an iterative decoding method.

FIG. 11 illustrates sample reception conditions.

FIG. 12 illustrates a further example of a transmission device applyinga phase changing method.

FIG. 13 illustrates yet a further example of a transmission deviceapplying a phase changing method.

FIGS. 14A and 14B illustrate another sample frame configuration.

FIGS. 15A and 15B illustrate another sample frame configuration.

FIGS. 16A and 16B illustrate another sample frame configuration.

FIGS. 17A and 17B illustrate another sample frame configuration.

FIGS. 18A and 18B illustrate another sample frame configuration.

FIGS. 19A and 19B illustrate examples of a mapping method.

FIGS. 20A and 20B illustrate further examples of a mapping method.

FIG. 21 illustrates a sample configuration of a weighting unit.

FIG. 22 illustrates a sample symbol rearrangement method.

FIG. 23 illustrates another example of a transmission and receptiondevice in a spatial multiplexing MIMO system.

FIGS. 24A and 24B illustrate sample BER characteristics.

FIG. 25 illustrates another sample phase changing method.

FIG. 26 illustrates another sample phase changing method.

FIG. 27 illustrates another sample phase changing method.

FIG. 28 illustrates another sample phase changing method.

FIG. 29 illustrates another sample phase changing method.

FIG. 30 illustrates a sample symbol arrangement for a modulated signalproviding high received signal quality.

FIG. 31 illustrates a sample frame configuration for a modulated signalproviding high received signal quality.

FIG. 32 illustrates a sample symbol arrangement for a modulated signalproviding high received signal quality.

FIG. 33 illustrates a sample symbol arrangement for a modulated signalproviding high received signal quality.

FIG. 34 illustrates a variation in numbers of symbols and slots neededper pair of coded blocks when block codes are used.

FIG. 35 illustrates another variation in numbers of symbols and slotsneeded per pair of coded blocks when block codes are used.

FIG. 36 illustrates an overall configuration of a digital broadcastingsystem.

FIG. 37 is a block diagram illustrating a sample receiver.

FIG. 38 illustrates multiplexed data configuration.

FIG. 39 is a schematic diagram illustrating multiplexing of encoded datainto streams.

FIG. 40 is a detailed diagram illustrating a video stream as containedin a PES packet sequence.

FIG. 41 is a structural diagram of TS packets and source packets in themultiplexed data.

FIG. 42 illustrates PMT data configuration.

FIG. 43 illustrates information as configured in the multiplexed data.

FIG. 44 illustrates the configuration of stream attribute information.

FIG. 45 illustrates the configuration of a video display and audiooutput device.

FIG. 46 illustrates a sample configuration of a communications system.

FIGS. 47A and 47B illustrate sample symbol arrangements for a modulatedsignal providing high received signal quality.

FIGS. 48A and 48B illustrate sample symbol arrangements for a modulatedsignal providing high received signal quality.

FIGS. 49A and 49B illustrate sample symbol arrangements for a modulatedsignal providing high received signal quality.

FIGS. 50A and 50B illustrate sample symbol arrangements for a modulatedsignal providing high received signal quality.

FIG. 51 illustrates a sample configuration of a transmission device.

FIG. 52 illustrates another sample configuration of a transmissiondevice.

FIG. 53 illustrates a further sample configuration of a transmissiondevice.

FIG. 54 illustrates yet a further sample configuration of a transmissiondevice.

FIG. 55 illustrates a baseband signal switcher.

FIG. 56 illustrates yet still a further sample configuration of atransmission device.

FIG. 57 illustrates sample operations of a distributor.

FIG. 58 illustrates further sample operations of a distributor.

FIG. 59 illustrates a sample communications system indicating therelationship between base stations and terminals.

FIG. 60 illustrates an example of transmit signal frequency allocation.

FIG. 61 illustrates another example of transmit signal frequencyallocation.

FIG. 62 illustrates a sample communications system indicating therelationship between a base station, repeaters, and terminals.

FIG. 63 illustrates an example of transmit signal frequency allocationwith respect to the base station.

FIG. 64 illustrates an example of transmit signal frequency allocationwith respect to the repeaters.

FIG. 65 illustrates a sample configuration of a receiver and transmitterin the repeater.

FIG. 66 illustrates a signal data format used for transmission by thebase station.

FIG. 67 illustrates yet still another sample configuration of atransmission device.

FIG. 68 illustrates another baseband signal switcher.

FIG. 69 illustrates a sample weighting, baseband signal switching, andphase changing method.

FIG. 70 illustrates a sample configuration of a transmission deviceusing an OFDM method.

FIGS. 71A and 71B illustrate another sample frame configuration.

FIG. 72 further illustrates the numbers of slots and phase changingvalues corresponding to a modulation scheme.

FIG. 73 further illustrates the numbers of slots and phase changingvalues corresponding to a modulation scheme.

FIG. 74 illustrates the overall frame configuration of a signaltransmitted by a broadcaster using DVB-T2.

FIG. 75 illustrates two or more types of signals at the same timestamp.

FIG. 76 illustrates still a further sample configuration of atransmission device.

FIG. 77 illustrates an alternate sample frame configuration.

FIG. 78 illustrates another alternate sample frame configuration.

FIG. 79 illustrates a further alternate sample frame configuration.

FIG. 80 illustrates yet a further alternate sample frame configuration.

FIG. 81 illustrates yet another alternate sample frame configuration.

FIG. 82 illustrates still another alternate sample frame configuration.

FIG. 83 illustrates still a further alternate sample frameconfiguration.

FIG. 84 further illustrates two or more types of signals at the sametimestamp.

FIG. 85 illustrates an alternate sample configuration of a transmissiondevice.

FIG. 86 illustrates an alternate sample configuration of a receptiondevice.

FIG. 87 illustrates another alternate sample configuration of areception device.

FIG. 88 illustrates yet another alternate sample configuration of areception device.

FIGS. 89A and 89B illustrate further alternate sample frameconfigurations.

FIGS. 90A and 90B illustrate yet further alternate sample frameconfigurations.

FIGS. 91A and 91B illustrate more alternate sample frame configurations.

FIGS. 92A and 92B illustrate yet more alternate sample frameconfigurations.

FIGS. 93A and 93B illustrate still further alternate sample frameconfigurations.

FIG. 94 illustrates a sample frame configuration used when space-timeblock codes are employed.

FIG. 95 illustrates an example of signal point distribution for 16-QAMin the I-Q plane.

FIG. 96 illustrates an example of signal point distribution for QPSK inthe I-Q plane.

FIG. 97 schematically shows absolute values of a log-likelihood ratioobtained by the reception device.

FIG. 98 schematically shows absolute values of a log-likelihood ratioobtained by the reception device.

FIG. 99 is an example of a structure of a signal processor pertaining toa weighting unit.

FIG. 100 is an example of a structure of the signal processor pertainingto the weighting unit.

FIG. 101 illustrates an example of signal point distribution for 64-QAMin the I-Q plane.

FIG. 102 illustrates an example of signal point distribution for 16-QAMin the I-Q plane.

FIG. 103 indicates a sample configuration for a signal generator whencyclic Q delay is applied.

FIG. 104 illustrates a first example of a generation method for s1(t)and s2(t) when cyclic Q delay is used.

FIG. 105 indicates a sample configuration for a signal generator whencyclic Q delay is applied.

FIG. 106 indicates a sample configuration for a signal generator whencyclic Q delay is applied.

FIG. 107 illustrates a second example of a generation method for s1(t)and s2(t) when cyclic Q delay is used.

FIG. 108 indicates a sample configuration for a signal generator whencyclic Q delay is applied.

FIG. 109 indicates a sample configuration for a signal generator whencyclic Q delay is applied.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described below with referenceto the accompanying drawings.

Embodiment 1

The following describes, in detail, a transmission method, atransmission device, a reception method, and a reception devicepertaining to the present Embodiment.

Before beginning the description proper, an outline of transmissionschemes and decoding schemes in a conventional spatial multiplexing MIMOsystem is provided.

FIG. 1 illustrates the structure of an Nt×Nr spatial multiplexing MIMOsystem. An information vector z is encoded and interleaved. The encodedbit vector u= . . . , u_(Nt)) is obtained as the interleave output.Here, u_(i)=(u_(i1), . . . , u_(iM)) (where M is the number oftransmitted bits per symbol). For a transmit vector s=(s_(i), . . . ,S_(Nt)), a received signal s_(i)=map(u_(i)) is found for transmitantenna #i. Normalizing the transmit energy, this is expressible asE{|s_(i)|²}=E_(s)/Nt (where E_(s) is the total energy per channel). Thereceive vector y=(y₁, . . . , y_(Nr))^(T) is expressed in Math. 1(formula 1), below.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 1} \rbrack & \; \\\begin{matrix}{y = ( {y_{1},\ldots \mspace{14mu},y_{Nr}} )^{T}} \\{= {{H_{NtNr}s} + n}}\end{matrix} & ( {{formula}\mspace{14mu} 1} )\end{matrix}$

Here, H_(NtNr) is the channel matrix, n=(n₁, . . . , n_(Nr)) is thenoise vector, and the average value of n_(i) is zero for independent andidentically distributed (i.i.d) complex Gaussian noise of variance σ².Based on the relationship between transmitted symbols introduced into areceiver and the received symbols, the probability distribution of thereceived vectors can be expressed as Math. 2 (formula 2), below, for amulti-dimensional Gaussian distribution.

$\begin{matrix}{\mspace{76mu} \lbrack {{Math}.\mspace{14mu} 2} \rbrack} & \; \\{\mspace{79mu} {{{p( y \middle| u )} = {\frac{1}{( {2{\pi\sigma}^{2}} )}\text{?}{\exp ( {{- \frac{1}{2\sigma^{2}}}{{y - {{Hs}(u)}}}^{2}} )}}}{\text{?}\text{indicates text missing or illegible when filed}}}} & ( {{formula}\mspace{14mu} 2} )\end{matrix}$

Here, a receiver performing iterative decoding is considered. Such areceiver is illustrated in FIG. 1 as being made up of an outersoft-in/soft-out decoder and a MIMO detector. The log-likelihood ratiovector (L-value) for FIG. 1 is given by Math. 3 (formula 3) throughMath. 5 (formula 5), as follows.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 3} \rbrack} & \; \\{\mspace{79mu} {{L(u)} = ( {{L( u_{1} )},\ldots \mspace{14mu},{L( {u\text{?}} )}} )^{T}}} & ( {{formula}\mspace{14mu} 3} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 4} \rbrack} & \; \\{\mspace{79mu} {{L( u_{i} )} = ( {{L( u_{i\; 1} )},\ldots \mspace{14mu},{L( u_{iM} )}} )}} & ( {{formula}\mspace{14mu} 4} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 5} \rbrack} & \; \\{\mspace{79mu} {{{L( u_{ij} )} = {\ln \frac{P( {u_{ij} = {+ 1}} )}{P( {u_{ij} = {- 1}} )}}}{\text{?}\text{indicates text missing or illegible when filed}}}} & ( {{formula}\mspace{14mu} 5} )\end{matrix}$

(Iterative Detection Method)

The following describes the MIMO signal iterative detection performed bythe N_(t)×N_(r) spatial multiplexing MIMO system. The log-likelihoodratio of u_(mn) is defined by Math. 6 (formula 6).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 6} \rbrack & \; \\{{L( u_{mn} \middle| y )} = {\ln \frac{P( {u_{mn} =  {+ 1} \middle| y } )}{P( {u_{mn} =  {- 1} \middle| y } )}}} & ( {{formula}\mspace{14mu} 6} )\end{matrix}$

Through application of Bayes' theorem, Math. 6 (formula 6) can beexpressed as Math. 7 (formula 7).

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 7} \rbrack} & \; \\{\begin{matrix}{{L( u_{mn} \middle| y )} = {\ln \frac{{p( { y \middle| u_{mn}  = {+ 1}} )}{{P( {u_{mn} = {+ 1}} )}/{p(y)}}}{{p( { y \middle| u_{mn}  = {- 1}} )}{{P( {u_{mn} = {- 1}} )}/{p(y)}}}}} \\{= {{\ln \frac{P( {u_{mn} = {+ 1}} )}{P( {u_{mn} = {- 1}} )}} + {\ln \frac{p( { y \middle| u_{mn}  = {+ 1}} )}{p( { y \middle| u_{mn}  = {- 1}} )}}}} \\{= {{\ln \frac{P( {u_{mn} = {+ 1}} )}{P( {u_{mn} = {- 1}} )}} + {\ln \frac{\sum{U\text{?}{p( y \middle| u )}{p( u \middle| u_{mn} )}}}{\sum{U\text{?}{p( y \middle| u )}{p( u \middle| u_{mn} )}}}}}}\end{matrix}{\text{?}\text{indicates text missing or illegible when filed}}} & ( {{formula}\mspace{14mu} 7} )\end{matrix}$

Note that U_(mn,±1)={u|u_(mn)=±1}. Through the approximation ln Σaj˜maxln a_(j), Math. 7 (formula 7) can be approximated as Math. 8 (formula8). The symbol˜is herein used to signify approximation.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 8} \rbrack \;} & \; \\{{L( u_{mn} \middle| y )} \approx {{\ln \frac{P( {u_{mn} = {+ 1}} )}{P( {u_{mn} = {- 1}} )}} + {\max\limits_{{Umn},{+ 1}}\{ {{\ln \; {p( y \middle| u )}} + {P( u \middle| u_{mn} )}} \}} - {\max\limits_{{Umn},{- 1}}\{ {{\ln \; {p( y \middle| u )}} + {P( u \middle| u_{mn} )}} \}}}} & ( {{formula}\mspace{14mu} 8} )\end{matrix}$

In Math. 8 (formula 8), P(u|u_(mn)) and ln P(u|u_(mn)) can be expressedas follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 9} \rbrack & \; \\\begin{matrix}{{P( u \middle| u_{mn} )} = {\prod\limits_{{({ij})} \neq {({mn})}}\; {P( u_{ij} )}}} \\{= {\prod\limits_{{({ij})} \neq {({mn})}}\frac{\exp ( \frac{u_{ij}{L( u_{ij} )}}{2} )}{{\exp ( \frac{L( u_{ij} )}{2} )} + {\exp ( {- \frac{L( u_{ij} )}{2}} )}}}}\end{matrix} & ( {{formula}\mspace{14mu} 9} ) \\\lbrack {{Math}.\mspace{14mu} 10} \rbrack & \; \\{{\ln \; {P( u \middle| u_{mn} )}} = {( {\sum\limits_{ij}{\ln \; {P( u_{ij} )}}} ) - {\ln \; {P( u_{mn} )}}}} & ( {{formula}\mspace{14mu} 10} ) \\\lbrack {{Math}.\mspace{14mu} 11} \rbrack & \; \\\begin{matrix}{{\ln \; {P( u_{ij} )}} = {{\frac{1}{2}u_{ij}{P( u_{ij} )}} - {\ln ( {{\exp ( \frac{L( u_{ij} )}{2} )} + {\exp ( {- \frac{L( u_{ij} )}{2}} )}} )}}} \\{\approx {{\frac{1}{2}u_{ij}{L( u_{ij} )}} - {\frac{1}{2}{{L( u_{ij} )}}\mspace{14mu} {for}\mspace{14mu} {{L( u_{ij} )}}}} > 2} \\{= {{\frac{L( u_{ij} )}{2}}( {{u_{ij}\mspace{14mu} {sign}\mspace{14mu} ( {L( u_{ij} )} )} - 1} )}}\end{matrix} & ( {{formula}\mspace{14mu} 11} )\end{matrix}$

Note that the log-probability of the equation given in Math. 2 (formula2) can be expressed as Math. 12 (formula 12).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 12} \rbrack & \; \\{{\ln \; {P( y \middle| u )}} = {{{- \frac{N_{r}}{2}}{\ln ( {2\pi \; \sigma^{2}} )}} - {\frac{1}{2\sigma^{2}}{{y - {{Hs}(u)}}}^{2}}}} & ( {{formula}\mspace{14mu} 12} )\end{matrix}$

Accordingly, given Math. 7 (formula 7) and Math. 13 (formula 13), theposterior L-value for the MAP or APP (a posteriori probability) can becan be expressed as follows.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 13} \rbrack} & \; \\{{{L( {\text{?}| y } )} = {\ln \frac{\text{?}\exp \{ {{{- \frac{1}{2\sigma^{2}}}{{y - {{Hs}(u)}}}^{2}} + {\sum\limits_{ij}{\ln \; {P( u_{ij} )}}}} \}}{\text{?}\exp \{ {{{- \frac{1}{2\sigma^{2}}}{{y - {{Hs}(u)}}}^{2}} + {\sum\limits_{ij}{\ln \; {P( u_{ij} )}}}} \}}}}{\text{?}\text{indicates text missing or illegible when filed}}} & ( {{formula}\mspace{14mu} 13} )\end{matrix}$

This is hereinafter termed iterative APP decoding. Also, given Math. 8(formula 8) and Math. 12 (formula 12), the posterior L-value for theMax-log APP can be can be expressed as follows.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 14} \rbrack} & \; \\{{L( u_{mn} \middle| y )} \approx {{\max\limits_{{Umn},{+ 1}}\{ {\Psi ( {u,y,{L(u)}} )} \}} - {\max\limits_{{Umn},{- 1}}\{ {\Psi ( {u,y,{L(u)}} )} \}}}} & ( {{formula}\mspace{14mu} 14} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 15} \rbrack} & \; \\{\mspace{79mu} {{\Psi ( {u,y,{L(u)}} )} = {{{- \frac{1}{2\sigma^{2}}}{{y - {{Hs}(u)}}}^{2}} + {\sum\limits_{ij}{\ln \; {P( u_{ij} )}}}}}} & ( {{formula}\mspace{14mu} 15} )\end{matrix}$

This is hereinafter referred to as iterative Max-log APP decoding. Assuch, the external information required by the iterative decoding systemis obtainable by subtracting prior input from Math. 13 (formula 13) orfrom Math. 14 (formula 14).

(System Model)

FIG. 23 illustrates the basic configuration of a system related to thefollowing explanations. The illustrated system is a 2×2 spatialmultiplexing MIMO system having an outer decoder for each of two streamsA and B. The two outer decoders perform identical LDPC encoding.(Although the present example considers a configuration in which theouter encoders use LDPC codes, the outer encoders are not restricted tothe use of LDPC as the error-correcting codes. The example may also berealized using other error-correcting codes, such as Turbo codes,convolutional codes, or LDPC convolutional codes. Further, while theouter encoders are presently described as individually configured foreach transmit antenna, no limitation is intended in this regard. Asingle outer encoder may be used for a plurality of transmit antennas,or the number of outer encoders may be greater than the number oftransmit antennas.) The system also has interleavers (π_(a), π_(b)) foreach of the streams A and B. Here, the modulation scheme is 2^(h)-QAM(i.e., h bits transmitted per symbol).

The receiver performs iterative detection (iterative APP (or Max-logAPP) decoding) of MIMO signals, as described above. The LDPC codes aredecoded using, for example, sum-product decoding.

FIG. 2 illustrates the frame configuration and describes the symbolorder after interleaving. Here, (i_(a),j_(a)) and (i_(b),j_(b)) can beexpressed as follows.

[Math. 16]

(i _(a) ,j _(a))=π_(a)(Q _(ia,ja) ^(a))  (formula 16)

[Math. 17]

(i _(b) ,j _(b))=π_(b)(Q _(ib,jb) ^(b))  (formula 17)

Here, i_(a), and i_(b) represent the symbol order after interleaving,j_(a) and j_(b) represent the bit position in the modulation scheme(where j_(a),j_(b)=1, h), π_(a) and π_(b) represent the interleavers ofstreams A and B, and Ω^(a) _(ia,ja) and Ω^(b) _(ib,jb) represent thedata order of streams A and B before interleaving. Note that FIG. 2illustrates a situation where i_(a)=i_(b).

(Iterative Decoding)

The following describes, in detail, the sum-product decoding used indecoding the LDPC codes and the MIMO signal iterative detectionalgorithm, both used by the receiver.

Sum-Product Decoding

A two-dimensional M×N matrix H={H_(mn)} is used as the check matrix forLDPC codes subject to decoding. For the set [1,N]={1, 2 . . . N}, thepartial sets A(m) and B(n) are defined as follows.

[Math. 18]

A(m)≡{n:H _(mn)=1}  (formula 18)

[Math. 19]

B(n)≡{m:H _(mn)=1}  (formula 19)

Here, A(m) signifies the set of column indices equal to 1 for row m ofcheck matrix H, while B(n) signifies the set of row indices equal to 1for row n of check matrix H. The sum-product decoding algorithm is asfollows.

Step A-1 (Initialization): For all pairs (m,n) satisfying H_(mn)=1, setthe prior log ratio β_(mn)=0. Set the loop variable (number ofiterations) 1_(sum)=1, and set the maximum number of loops 1_(sum,max).Step A-2 (Processing): For all pairs (m,n) satisfying H_(mn)=1 in theorder m=1, 2, . . . M, update the extrinsic value log ratio α_(mn) usingthe following update formula.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 20} \rbrack} & \; \\{\alpha_{mn} = {( {\prod\limits_{n^{\prime} \in {{A{(m)}}{\backslash n}}}\; {{sign}\; ( {\lambda_{n^{\prime}} + \beta_{{mn}^{\prime}}} )}} ) \times {f( {\sum\limits_{n^{\prime} \in {{A{(m)}}{\backslash n}}}{f( {\lambda_{n^{\prime}} + \beta_{{mn}^{\prime}}} )}} )}}} & ( {{formula}\mspace{14mu} 20} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 21} \rbrack} & \; \\{\mspace{79mu} {{{sign}(x)} \equiv \{ \begin{matrix}1 & {x \geq 0} \\{- 1} & {x < 0}\end{matrix} }} & ( {{formula}\mspace{14mu} 21} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 22} \rbrack} & \; \\{\mspace{79mu} {{f(x)} \equiv {\ln \frac{{\exp (x)} + 1}{{\exp (x)} - 1}}}} & ( {{formula}\mspace{14mu} 22} )\end{matrix}$

where ƒ is the Gallager function. λ_(n) can then be computed as follows.

Step A-3 (Column Operations): For all pairs (m,n) satisfying H_(mn)=1 inthe order n=1, 2, . . . N, update the extrinsic value log ratio β_(mn)using the following update formula.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 23} \rbrack & \; \\{\beta_{mn} = {\sum\limits_{m^{\prime} \in {{B{(n)}}\backslash m}}\alpha_{m^{\prime}n}}} & ( {{formula}\mspace{14mu} 23} )\end{matrix}$

Step A-4 (Log-likelihood Ratio Calculation): For nε[1,N], thelog-likelihood ratio L_(n) is computed as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 24} \rbrack & \; \\{L_{n} = {{\sum\limits_{m^{\prime} \in {{B{(n)}}\backslash m}}\alpha_{m^{\prime}n}} + \lambda_{n}}} & ( {{formula}\mspace{14mu} 24} )\end{matrix}$

Step A-5 (Iteration Count): If 1_(sum)<1_(sum,max), then 1_(sum) isincremented and the process returns to step A-2. Sum-product decodingends when 1_(mn)=1_(sum,max).

The above describes one iteration of sum-product decoding operations.Afterward, MIMO signal iterative detection is performed. The variablesm, n, α_(mn), β_(mn), λ_(n), and L_(n) used in the above explanation ofsum-product decoding operations are expressed as m_(a), n_(a), α^(a)_(mana), β^(a) _(mana), λ_(na), and L_(na) for stream A and as m_(b),n_(b), α^(b) _(mbnb), β^(b) _(mbnb), λ_(nb), and L_(nb) for stream B.

(MIMO Signal Iterative Detection)

The following describes the calculation of λ_(n) for MIMO signaliterative detection.

The following formula is derivable from Math. 1 (formula 1).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 25} \rbrack & \; \\\begin{matrix}{{y(t)} = ( {{y_{1}(t)},{y_{2}(t)}} )^{T}} \\{= {{{H_{22}(t)}{s(t)}} + {n(t)}}}\end{matrix} & ( {{formula}\mspace{14mu} 25} )\end{matrix}$

Given the frame configuration illustrated in FIG. 2, the followingfunctions are derivable from Math. 16 (formula 16) and Math. 17 (formula17).

[Math. 26]

n _(a)=Ω_(ia,ja) ^(a)  (formula 26)

[Math. 27]

n _(b)=Ω_(ib,jb) ^(b)  (formula 27)

where n_(a),n_(b) ε[1,N]. For iteration k of MIMO signal iterativedetection, the variables λ_(na), L_(na), λ_(nb), and L_(nb) areexpressed as λ_(k,na), L_(k,na), λ_(κ,nb), and L_(k,ab).

Step B-1 (Initial Detection; k=0) For initial wave detection, λ_(o,na)and λ_(0,nb) are calculated as follows.For iterative APP decoding:

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 28} \rbrack} & \; \\{{\text{?} = {\ln \frac{\text{?}\exp \{ {{- \frac{1}{2\sigma^{2}}}{{{y( i_{X} )} - {{H_{22}( i_{X} )}{s(u)}( i_{X} )}}}^{2}} \}}{\text{?}\exp \{ {{- \frac{1}{2\sigma^{2}}}{{{y( i_{X} )} - {{H_{22}( i_{X} )}{s(u)}( i_{X} )}}}^{2}} \}}}}{\text{?}\text{indicates text missing or illegible when filed}}} & ( {{formula}\mspace{14mu} 28} )\end{matrix}$

For iterative Max-log APP decoding:

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 29} \rbrack} & \; \\{\text{?} = {{\text{?}\{ {\Psi ( {{u( i_{X} )},{y( i_{X} )}} )} \}} - {\text{?}\{ {\Psi ( {{u( i_{X} )},{y( i_{X} )}} )} \}}}} & ( {{formula}\mspace{14mu} 29} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 30} \rbrack} & \; \\{\mspace{79mu} {{{\Psi ( {{u( i_{X} )},{y( i_{X} )}} )} = {{- \frac{1}{2\sigma^{2}}}{{{y( i_{X} )} - {{H_{22}( i_{X} )}{s( {u( i_{X} )} )}}}}^{2}}}{\text{?}\text{indicates text missing or illegible when filed}}}} & ( {{formula}\mspace{14mu} 30} )\end{matrix}$

where X=a,b. Next, the iteration count for the MIMO signal iterativedetection is set to 1_(mimo)=0, with the maximum iteration count being1_(mimo,max).

Step B-2 (Iterative Detection; Iteration k): When the iteration count isk, Math. 11 (formula 11), Math. 13 (formula 13) through Math. 15(formula 15), Math. 16 (formula 16), and Math. 17 (formula 17) can beexpressed as Math. 31 (formula 31) through Math. 34 (formula 34), below.Note that (X,Y)=(a,b)(b,a).For iterative APP decoding:

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 31} \rbrack} & \; \\{\text{?} = {{\text{?}( \text{?} )} + {\ln \frac{\text{?}\exp \{ {{{- \frac{1}{2\sigma^{2}}}{{{y( i_{X} )} - {{H_{22}( i_{X} )}{s(u)}( i_{X} )}}}^{2}} + {\rho ( \text{?} )}} \}}{\text{?}\exp \{ {{{- \frac{1}{2\sigma^{2}}}{{{y( i_{X} )} - {{H_{22}( i_{X} )}{s(u)}( i_{X} )}}}^{2}} + {\rho ( \text{?} )}} \}}}}} & ( {{formula}\mspace{14mu} 31} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 32} \rbrack} & \; \\{{{\rho ( \text{?} )} = {{\sum\limits_{\underset{y \neq {j\; X}}{y = 1}}^{h}{{\frac{\text{?}}{2}}( {{\text{?}{{sign}( {\text{?}( \text{?} )} )}} - 1} )}} + {\sum\limits_{y = 1}^{h}{{\frac{\text{?}}{2}}( {{\text{?}{{sign}( {\text{?}( \text{?} )} )}} - 1} )}}}}{\text{?}\text{indicates text missing or illegible when filed}}} & ( {{formula}\mspace{14mu} 32} )\end{matrix}$

For iterative Max-log APP decoding:

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 33} \rbrack} & \; \\{\text{?} = {{\text{?}( \text{?} )} + {\text{?}\{ {\Psi ( {{u( i_{X} )},{y( i_{X} )},{\rho ( \text{?} )}} )} \}} - {\text{?}\{ {\Psi ( {{u( i_{X} )},{y( i_{X} )},{\rho ( \text{?} )}} )} \}}}} & ( {{formula}\mspace{14mu} 33} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 34} \rbrack} & \; \\{{{\Psi ( {{u( i_{X} )},{y( i_{X} )},{\rho ( \text{?} )}} )} = {{{- \frac{1}{2\sigma^{2}}}{{{y( i_{X} )} - {{H_{22}( i_{X} )}{s( {u( i_{X} )} )}}}}^{2}} + {\rho ( \text{?} )}}}{\text{?}\text{indicates text missing or illegible when filed}}} & ( {{formula}\mspace{14mu} 34} )\end{matrix}$

Step B-3 (Iteration Count and Codeword Estimation) If1_(mimo)<1_(mimo,max), then 1_(mimo) is incremented and the processreturns to step B-2. When 1_(mimo)=1_(mimo,max), an estimated codewordis found, as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 35} \rbrack & \; \\{{\hat{u}}_{n_{x}} = \{ \begin{matrix}1 & {L_{l_{mino},n_{x}} \geq 0} \\{- 1} & {L_{l_{mino},n_{x}} < 0}\end{matrix} } & ( {{formula}\mspace{14mu} 35} )\end{matrix}$

where X=a,b.

FIG. 3 shows a sample configuration of a transmission device 300pertaining to the present Embodiment. An encoder 302A takes information(data) 301A and a frame configuration signal 313 as input (whichincludes the error-correction method, coding rate, block length, andother information used by the encoder 302A in error-correction coding ofthe data, such that the method designated by the frame configurationsignal 313 is used. The error-correction method may be switched). Inaccordance with the frame configuration signal 313, the encoder 302Aperforms error-correction coding, such as convolutional encoding, LDPCencoding, turbo encoding or similar, and outputs encoded data 303A.

An interleaver 304A takes the encoded data 303A and the frameconfiguration signal 313 as input, performs interleaving, i.e.,rearranges the order thereof, and then outputs interleaved data 305A.(Depending on the frame configuration signal 313, the interleavingmethod may be switched.)

A mapper 306A takes the interleaved data 305A and the frameconfiguration signal 313 as input and performs modulation, such as(Quadrature Phase Shift Keying), 16-QAM (16-Quadradature AmplitudeModulation), or 64-QAM (64-Quadradture Amplitude Modulation) thereon,then outputs a baseband signal 307A. (Depending on the frameconfiguration signal 313, the modulation scheme may be switched.)

FIGS. 19A and 19B illustrate an example of a QPSK modulation mappingmethod for a baseband signal made up of an in-phase component I and aquadrature component Q in the I-Q plane. For example, as shown in FIG.19A, when the input data are 00, then the output is I=1.0, Q=1.0.Similarly, when the input data are 01, the output is I=−1.0, Q=1.0, andso on. FIG. 19B illustrates an example of a QPSK modulation mappingmethod in the I-Q plane differing from FIG. 19A in that the signalpoints of FIG. 19A have been rotated about the origin to obtain thesignal points of FIG. 19B. Non-Patent Literature 9 and Non-PatentLiterature 10 describe such a constellation rotation method.Alternatively, the Cyclic Q Delay described in Non-Patent Literature 9and Non-Patent Literature 10 may also be adopted. An alternate example,distinct from FIGS. 19A and 19B, is shown in FIGS. 20A and 20B, whichillustrate signal point distribution for 16-QAM in the I-Q plane. Theexample of FIG. 20A corresponds to FIG. 19A, while that of FIG. 20Bcorresponds to FIG. 19B.

An encoder 302B takes information (data) 301B and the frameconfiguration signal 313 as input (which includes the error-correctionmethod, coding rate, block length, and other information used by theencoder 302B in error-correction coding of the data, such that themethod designated by the frame configuration signal 313 is used. Theerror-correction method may be switched). In accordance with the frameconfiguration signal 313, the encoder 302B performs error-correctioncoding, such as convolutional encoding, LDPC encoding, turbo encoding orsimilar, and outputs encoded data 303B.

An interleaver 304B takes the encoded data 303B and the frameconfiguration signal 313 as input, performs interleaving, i.e.,rearranges the order thereof, and outputs interleaved data 305B.(Depending on the frame configuration signal 313, the interleavingmethod may be switched.)

A mapper 306B takes the interleaved data 305B and the frameconfiguration signal 313 as input and performs modulation, such as QPSK,16-QAM, or 64-QAM thereon, then outputs a baseband signal 307B.(Depending on the frame configuration signal 313, the modulation schememay be switched.)

A signal processing method information generator 314 takes the frameconfiguration signal 313 as input and accordingly outputs signalprocessing method information 315. The signal processing methodinformation 315 designates the fixed precoding matrix to be used, andincludes information on the pattern of phase changes used for changingthe phase.

A weighting unit 308A takes baseband signal 307A, baseband signal 307B,and the signal processing method information 315 as input and, inaccordance with the signal processing method information 315, performsweighting on the baseband signals 307A and 307B, then outputs a weightedsignal 309A. The weighting method is described in detail, later.

A wireless unit 310A takes weighted signal 309A as input and performsprocessing such as quadrature modulation, band limitation, frequencyconversion, amplification, and so on, then outputs transmit signal 311A.Transmit signal 311A is then output as radio waves by an antenna 312A.

A weighting unit 308B takes baseband signal 307A, baseband signal 307B,and the signal processing method information 315 as input and, inaccordance with the signal processing method information 315, performsweighting on the baseband signals 307A and 307B, then outputs weightedsignal 316B.

FIG. 21 illustrates the configuration of the weighting units 308A and308B. The area of FIG. 21 enclosed in the dashed line represents one ofthe weighting units. Baseband signal 307A is multiplied by w11 to obtainw11·s1(t), and multiplied by w21 to obtain w21·s1(t). Similarly,baseband signal 307B is multiplied by w12 to obtain w12·s2(t), andmultiplied by w22 to obtain w22·s2(t). Next, z1(t)=w11·s1(t)+w12·s2(t)and z2(t)=w21·s1(t)+w22·s22(t) are obtained. Here, as explained inEmbodiment 1, s1(t) and s2(t) are baseband signals modulated accordingto a modulation scheme such as BPSK (Binary Phase Shift Keying), QPSK,8-PSK (8-Phase Shift Keying), 16-QAM, 32-QAM (32-Quadrature AmplitudeModulation), 64-QAM, 256-QAM 16-APSK (16-Amplitude Phase Shift Keying)and so on.

Both weighting units perform weighting using a fixed precoding matrix.The precoding matrix uses, for example, the method of Math. 36 (formula36), and satisfies the conditions of Math. 37 (formula 37) or Math. 38(formula 38), all found below. However, this is only an example. Thevalue of α is not restricted to Math. 37 (formula 37) and Math. 38(formula 38), and may take on other values, e.g., α=1.

Here, the precoding matrix is

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 36} \rbrack & \; \\{\begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix} = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j\; 0} & {\alpha \times ^{j\; 0}} \\{\alpha \times ^{j\; 0}} & ^{j\; \pi}\end{pmatrix}}} & ( {{formula}\mspace{14mu} 36} )\end{matrix}$

In Math. 36 (formula 36), above, α is given by:

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 37} \rbrack & \; \\{\alpha = \frac{\sqrt{2} + 4}{\sqrt{2} + 2}} & ( {{formula}\mspace{14mu} 37} )\end{matrix}$

Alternatively, in Math. 36 (formula 36), above, α may be given by:

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 38} \rbrack & \; \\{\alpha = \frac{\sqrt{2} + 3 + \sqrt{5}}{\sqrt{2} + 3 - \sqrt{5}}} & ( {{formula}\mspace{14mu} 38} )\end{matrix}$

The precoding matrix is not restricted to that of Math. 36 (formula 36),but may also be as indicated by Math. 39 (formula 39).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 39} \rbrack & \; \\{\begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix} = \begin{pmatrix}a & b \\c & d\end{pmatrix}} & ( {{formula}\mspace{14mu} 39} )\end{matrix}$

In Math. 39 (formula 39), let a=Ae^(jδ11), b=Be^(jδ12), c=Ce^(jδ21), andd=De^(jδ22). Further, one of a, b, c, and d may be equal to zero. Forexample, the following configurations are possible: (1) a may be zerowhile b, c, and d are non-zero, (2) b may be zero while a, c, and d arenon-zero, (3) c may be zero while a, b, and d are non-zero, or (4) d maybe zero while a, b, and c are non-zero.

When any of the modulation scheme, error-correcting codes, and thecoding rate thereof are changed, the precoding matrix may also be set,changed, and fixed for use.

A phase changer 317B takes weighted signal 316B and the signalprocessing method information 315 as input, then regularly changes thephase of the signal 316B for output. This regular change is a change ofphase performed according to a predetermined phase changing patternhaving a predetermined period (cycle) (e.g., every n symbols (n being aninteger, n≧1) or at a predetermined interval). The details of the phasechanging pattern are explained below, in Embodiment 4.

Wireless unit 310B takes post-phase change signal 309B as input andperforms processing such as quadrature modulation, band limitation,frequency conversion, amplification, and so on, then outputs transmitsignal 311B. Transmit signal 311B is then output as radio waves by anantenna 312B.

FIG. 4 illustrates a sample configuration of a transmission device 400that differs from that of FIG. 3. The points of difference of FIG. 4from FIG. 3 are described next.

An encoder 402 takes information (data) 401 and the frame configurationsignal 313 as input, and, in accordance with the frame configurationsignal 313, performs error-correction coding and outputs encoded data402.

A distributor 404 takes the encoded data 403 as input, performsdistribution thereof, and outputs data 405A and data 405B. Although FIG.4 illustrates only one encoder, the number of encoders is not limited assuch. The present invention may also be realized using m encoders (mbeing an integer, m≧1) such that the distributor divides the encodeddata created by each encoder into two groups for distribution.

FIG. 5 illustrates an example of a frame configuration in the timedomain for a transmission device according to the present Embodiment.Symbol 500_1 is a symbol for notifying the reception device of thetransmission scheme. For example, symbol 500_1 conveys information suchas the error-correction method used for transmitting data symbols, thecoding rate thereof, and the modulation scheme used for transmittingdata symbols.

Symbol 501_1 is for estimating channel fluctuations for modulated signalz1(t) (where t is time) transmitted by the transmission device. Symbol502_1 is a data symbol transmitted by modulated signal z1(t) as symbolnumber u (in the time domain). Symbol 503_1 is a data symbol transmittedby modulated signal z1(t) as symbol number u+1.

Symbol 501_2 is for estimating channel fluctuations for modulated signalz2(t) (where t is time) transmitted by the transmission device. Symbol502_2 is a data symbol transmitted by modulated signal z2(t) as symbolnumber u. Symbol 503_2 is a data symbol transmitted by modulated signalz1(t) as symbol number u+1.

Here, the symbols of z1(t) and of z2(t) having the same timestamp(identical timing) are transmitted from the transmit antenna using thesame (shared/common) frequency.

The following describes the relationships between the modulated signalsz1 (t) and z2(t) transmitted by the transmission device and the receivedsignals r1(t) and r2(t) received by the reception device.

In FIG. 5, 504#1 and 504#2 indicate transmit antennas of thetransmission device, while 505#1 and 505#2 indicate receive antennas ofthe reception device. The transmission device transmits modulated signalz1(t) from transmit antenna 504#1 and transmits modulated signal z2(t)from transmit antenna 504#2. Here, modulated signals z1(t) and z2(t) areassumed to occupy the same (shared/common) frequency (bandwidth). Thechannel fluctuations in the transmit antennas of the transmission deviceand the antennas of the reception device are h₁₁(t), h₁₂(t), h₂₁(t), andh₂₂(t), respectively. Assuming that receive antenna 505#1 of thereception device receives received signal r1(t) and that receive antenna505#2 of the reception device receives received signal r2(t), thefollowing relationship holds.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 40} \rbrack & \; \\{\begin{pmatrix}{r\; 1(t)} \\{r\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h_{11}(t)} & {h_{12}(t)} \\{h_{21}(t)} & {h_{22}(t)}\end{pmatrix}\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix}}} & ( {{formula}\mspace{14mu} 40} )\end{matrix}$

FIG. 6 pertains to the weighting method (precoding method) and the phasechanging method of the present Embodiment. A weighting unit 600 is acombined version of the weighting units 308A and 308B from FIG. 3. Asshown, stream s1(t) and stream s2(t) correspond to the baseband signals307A and 307B of FIG. 3. That is, the streams s1(t) and s2(t) arebaseband signals made up of an in-phase component I and a quadraturecomponent Q conforming to mapping by a modulation scheme such as QPSK,16-QAM, and 64-QAM. As indicated by the frame configuration of FIG. 6,stream s1(t) is represented as s1(u) at symbol number u, as s1(u+1) atsymbol number u+1, and so forth. Similarly, stream s2(t) is representedas s2(u) at symbol number u, as s2(u+1) at symbol number u+1, and soforth. The weighting unit 600 takes the baseband signals 307A (s1(t))and 307B (s2(t)) as well as the signal processing method information 315from FIG. 3 as input, performs weighting in accordance with the signalprocessing method information 315, and outputs the weighted signals 309A(z1(t)) and 316B(z2′(t)) from FIG. 3. The phase changer 317B changes thephase of weighted signal 316B(z2′(t)) and outputs post-phase changesignal 309B(z2(t)).

Here, given vector W1=(w11,w12) from the first row of the fixedprecoding matrix F, z1(t) is expressible as Math. 41 (formula 41),below.

[Math. 41]

z1(t)=W1×(s1(t),s2(t))^(T)  (formula 41)

Similarly, given vector W2=(w21,w22) from the second row of the fixedprecoding matrix F, and letting the phase changing formula applied bythe phase changer by y(t), then z2(t) is expressible as Math. 42(formula 42), below.

[Math. 42]

z2(t)=y(t)×W2×(s1(t),s2(t))^(T)  (formula 42)

Here, y(t) is a phase changing formula obeying a predetermined method.For example, given a period (cycle) of four and timestamp u, the phasechanging formula may be expressed as Math. 43 (formula 43), below.

[Math. 43]

y(u)=e ^(j0)  (formula 43)

Similarly, the phase changing formula for timestamp u+1 may be, forexample, as given by Math. 44 (formula 44).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} {44}} \rbrack & \; \\{{y( {u + 1} )} = ^{j\frac{\pi}{2}}} & ( {{formula}\mspace{14mu} 44} )\end{matrix}$

That is, the phase changing formula for timestamp u+k generalizes toMath. 45 (formula 45).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} {45}} \rbrack & \; \\{{y( {u + k} )} = ^{j\frac{k\; \pi}{2}}} & ( {{formula}\mspace{14mu} 45} )\end{matrix}$

Note that Math. 43 (formula 43) through Math. 45 (formula 45) are givenonly as an example of a regular change of phase.

The regular change of phase is not restricted to a period (cycle) offour.

Improved reception capabilities (the error-correction capabilities, tobe exact) may potentially be promoted in the reception device byincreasing the period (cycle) number (this does not mean that a greaterperiod (cycle) is better, though avoiding small numbers such as two islikely ideal).

Furthermore, although Math. 43 (formula 43) through Math. 45 (formula45), above, represent a configuration in which a change in phase iscarried out through rotation by consecutive predetermined phases (in theabove formula, every π/2), the change in phase need not be rotation by aconstant amount, but may also be random. For example, in accordance withthe predetermined period (cycle) of y(t), the phase may be changedthrough sequential multiplication as shown in Math. 46 (formula 46) andMath. 47 (formula 47). The key point of the regular change of phase isthat the phase of the modulated signal is regularly changed. The phasechanging degree variance rate is preferably as even as possible, such asfrom −π radians to π radians. However, given that this concerns adistribution, random variance is also possible.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} {46}} \rbrack} & \; \\ ^{j0}arrow ^{j\frac{\pi}{5}}arrow ^{j\frac{2\pi}{5}}arrow ^{j\frac{3\pi}{5}}arrow ^{j\frac{4\pi}{5}}arrow ^{j\pi}arrow ^{j\frac{6\pi}{5}}arrow ^{j\frac{7\pi}{5}}arrow ^{j\frac{8\pi}{5}}arrow ^{j\frac{9\pi}{5}}          & ( {{formula}\mspace{14mu} 46} ) \\{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} {47}} \rbrack} & \; \\ ^{j\frac{\pi}{2}}arrow ^{j\pi}arrow ^{j\frac{3\pi}{2}}arrow ^{j2\pi}arrow ^{j\frac{\pi}{4}}arrow ^{j\frac{3}{4}\pi}arrow ^{j\frac{5\pi}{4}}arrow ^{j\frac{7\pi}{4}}        & ( {{formula}\mspace{14mu} 47} )\end{matrix}$

As such, the weighting unit 600 of FIG. 6 performs precoding usingfixed, predetermined precoding weights, and the phase changer 317Bchanges the phase of the signal input thereto while regularly varyingthe phase changing degree.

When a specialized precoding matrix is used in the LOS environment, thereception quality is likely to improve tremendously. However, dependingon the direct wave conditions, the phase and amplitude components of thedirect wave may greatly differ from the specialized precoding matrix,upon reception. The LOS environment has certain rules. Thus, datareception quality is tremendously improved through a regular change oftransmit signal phase that obeys those rules.

The present invention offers a signal processing method for improvingthe LOS environment.

FIG. 7 illustrates a sample configuration of a reception device 700pertaining to the present embodiment. Wireless unit 703_X receives, asinput, received signal 702_X received by antenna 701_X, performsprocessing such as frequency conversion, quadrature demodulation, andthe like, and outputs baseband signal 704_X.

Channel fluctuation estimator 705_1 for modulated signal z1 transmittedby the transmission device takes baseband signal 704_X as input,extracts reference symbol 501_1 for channel estimation from FIG. 5,estimates the value of h₁₁ from Math. 40 (formula 40), and outputschannel estimation signal 706_1.

Channel fluctuation estimator 705_2 for modulated signal z2 transmittedby the transmission device takes baseband signal 704_X as input,extracts reference symbol 502_2 for channel estimation from FIG. 5,estimates the value of h₁₂ from Math. 40 (formula 40), and outputschannel estimation signal 706_1.

Wireless unit 703_Y receives, as input, received signal 702_Y receivedby antenna 701_Y, performs processing such as frequency conversion,quadrature demodulation, and the like, and outputs baseband signal704_Y.

Channel fluctuation estimator 707_1 for modulated signal z1 transmittedby the transmission device takes baseband signal 704_Y as input,extracts reference symbol 501_1 for channel estimation from FIG. 5,estimates the value of h₁₁ from Math. 40 (formula 40), and outputschannel estimation signal 708_1.

Channel fluctuation estimator 707_2 for modulated signal z2 transmittedby the transmission device takes baseband signal 704_Y as input,extracts reference symbol 502_2 for channel estimation from FIG. 5,estimates the value of h₁₁ from Math. 40 (formula 40), and outputschannel estimation signal 708_2.

A control information decoder 709 receives baseband signal 704_X andbaseband signal 704_Y as input, detects symbol 500_1 that indicates thetransmission scheme from FIG. 5, and outputs a transmission methodinformation signal 710 for the transmission device.

A signal processor 711 takes the baseband signals 704_X and 704_Y, thechannel estimation signals 706_1, 706_2, 708_1, and 708_2, and thetransmission method information signal 710 as input, performs detectionand decoding, and then outputs received data 712_1 and 712_2.

Next, the operations of the signal processor 711 from FIG. 7 aredescribed in detail. FIG. 8 illustrates a sample configuration of thesignal processor 711 pertaining to the present embodiment. As shown, thesignal processor 711 is primarily made up of an inner MIMO detector, asoft-in/soft-out decoder, and a coefficient generator. Non-PatentLiterature 2 and Non-Patent Literature 3 describe the method ofiterative decoding with this structure. The MIMO system described inNon-Patent Literature 2 and Non-Patent Literature 3 is a spatialmultiplexing MIMO system, while the present Embodiment differs fromNon-Patent Literature 2 and Non-Patent Literature 3 in describing a MIMOsystem that regularly changes the phase over time, while using theprecoding matrix. Taking the (channel) matrix H(t) of Math. 36 (formula36), then by letting the precoding weight matrix from FIG. 6 be F (here,a fixed precoding matrix remaining unchanged for a given receivedsignal) and letting the phase changing formula used by the phase changerfrom FIG. 6 be Y(t) (here, Y(t) changes over time t), then the receivevector R(t)=(r1(t),r2(t))^(T) and the stream vectorS(t)=(s1(t),s2(t))^(T) the following function is derived:

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} {48}} \rbrack & \; \\{{{R(t)} = {{H(t)} \times {Y(t)} \times F \times {S(t)}}}{where}{{Y(t)} = \begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}}} & ( {{formula}\mspace{14mu} 48} )\end{matrix}$

Here, the reception device may use the decoding methods of Non-PatentLiterature 2 and 3 on R(t) by computing H(t)×Y(t)×F.

Accordingly, the coefficient generator 819 from FIG. 8 takes atransmission method information signal 818 (corresponding to 710 fromFIG. 7) indicated by the transmission device (information for specifyingthe fixed precoding matrix in use and the phase changing pattern usedwhen the phase is changed) and outputs a signal processing methodinformation signal 820.

The inner MIMO detector 803 takes the signal processing methodinformation signal 820 as input and performs iterative detection anddecoding using the signal and the relationship thereof to Math. 48(formula 48). The operations thereof are described below.

The processing unit illustrated in FIG. 8 must use a processing method,as is illustrated in FIG. 10, to perform iterative decoding (iterativedetection). First, detection of one codeword (or one frame) of modulatedsignal (stream) s1 and of one codeword (or one frame) of modulatedsignal (stream) s2 are performed. As a result, the soft-in/soft-outdecoder obtains the log-likelihood ratio of each bit of the codeword (orframe) of modulated signal (stream) s1 and of the codeword (or frame) ofmodulated signal (stream) s2. Next, the log-likelihood ratio is used toperform a second round of detection and decoding. These operations(referred to as iterative decoding (iterative detection)) are performedmultiple times. The following explanations centre on the creation methodof the log-likelihood ratio of a symbol at a specific time within oneframe.

In FIG. 8, a memory 815 takes baseband signal 801X (corresponding tobaseband signal 704_X from FIG. 7), channel estimation signal group 802X(corresponding to channel estimation signals 706_1 and 706_2 from FIG.7), baseband signal 801Y (corresponding to baseband signal 704_Y fromFIG. 7), and channel estimation signal group 802Y (corresponding tochannel estimation signals 708_1 and 708_2 from FIG. 7) as input,executes (computes) H(t)×Y(t)×F from Math. 48 (formula 48) in order toperform iterative decoding (iterative detection), and stores theresulting matrix as a transformed channel signal group. The memory 815then outputs the above-described signals as needed, specifically asbaseband signal 816X, transformed channel estimation signal group 817X,baseband signal 816Y, and transformed channel estimation signal group817Y.

Subsequent operations are described separately for initial detection andfor iterative decoding (iterative detection).

(Initial Detection)

The inner MIMO detector 803 takes baseband signal 801X, channelestimation signal group 802X, baseband signal 801Y, and channelestimation signal group 802Y as input. Here, the modulation scheme formodulated signal (stream) s1 and modulated signal (stream) s2 isdescribed as 16-QAM.

The inner MIMO detector 803 first computes H(t)×Y(t)×F from the channelestimation signal groups 802X and 802Y, thus calculating a candidatesignal point corresponding to baseband signal 801X. FIG. 11 representssuch a calculation. In FIG. 11, each black dot is a candidate signalpoint in the I-Q plane. Given that the modulation scheme is 16-QAM, 256candidate signal points exist. (However, FIG. 11 is only arepresentation and does not indicate all 256 candidate signal points.)Letting the four bits transmitted in modulated signal s1 be b0, b1, b2,and b3 and the four bits transmitted in modulated signal s2 be b4, b5,b6, and b7, candidate signal points corresponding to (b0, b1, b2, b3,b4, b5, b6, b7) are found in FIG. 11. The Euclidean squared distancebetween each candidate signal point and each received signal point 1101(corresponding to baseband signal 801X) is then computed. The Euclidiansquared distance between each point is divided by the noise variance σ².Accordingly, E_(X)(b0, b1, b2, b3, b4, b5, b6, b7) is calculated. Thatis, the Euclidian squared distance between a candidate signal pointcorresponding to (b0, b1, b2, b3, b4, b5, b6, b7) and a received signalpoint is divided by the noise variance. Here, each of the basebandsignals and the modulated signals s1 and s2 is a complex signal.

Similarly, the inner MIMO detector 803 computes H(t)×Y(t)×F from thechannel estimation signal groups 802X and 802Y, calculates candidatesignal points corresponding to baseband signal 801Y, computes theEuclidean squared distance between each of the candidate signal pointsand the received signal points (corresponding to baseband signal 801Y),and divides the Euclidean squared distance by the noise variance σ².Accordingly, E_(Y)(b0, b1, b2, b3, b4, b5, b6, b7) is calculated. Thatis, E_(Y) is the Euclidian squared distance between a candidate signalpoint corresponding to (b0, b1, b2, b3, b4, b5, b6, b7) and a receivedsignal point, divided by the noise variance.

Next, E_(X)(b0, b1, b2, b3, b4, b5, b6, b7)+E_(Y)(b0, b1, b2, b3, b4,b5, b6, b7)=E(b0, b1, b2, b3, b4, b5, b6, b7) is computed.

The inner MIMO detector 803 outputs E(b0, b1, b2, b3, b4, b5, b6, b7) asthe signal 804.

The log-likelihood calculator 805A takes the signal 804 as input,calculates the log-likelihood of bits b0, b1, b2, and b3, and outputsthe log-likelihood signal 806A. Note that this log-likelihoodcalculation produces the log-likelihood of a bit being 1 and thelog-likelihood of a bit being 0. The calculation method is as shown inMath. 28 (formula 28), Math. 29 (formula 29), and Math. 30 (formula 30),and the details thereof are given by Non-Patent Literature 2 and 3.

Similarly, log-likelihood calculator 805B takes the signal 804 as input,calculates the log-likelihood of bits b4, b5, b6, and b7, and outputslog-likelihood signal 806B.

A deinterleaver (807A) takes log-likelihood signal 806A as input,performs deinterleaving corresponding to that of the interleaver (theinterleaver (304A) from FIG. 3), and outputs deinterleavedlog-likelihood signal 808A.

Similarly, a deinterleaver (807B) takes log-likelihood signal 806B asinput, performs deinterleaving corresponding to that of the interleaver(the interleaver (304B) from FIG. 3), and outputs deinterleavedlog-likelihood signal 808B.

Log-likelihood ratio calculator 809A takes deinterleaved log-likelihoodsignal 808A as input, calculates the log-likelihood ratio of the bitsencoded by encoder 302A from FIG. 3, and outputs log-likelihood ratiosignal 810A.

Similarly, log-likelihood ratio calculator 809B takes deinterleavedlog-likelihood signal 808B as input, calculates the log-likelihood ratioof the bits encoded by encoder 302B from FIG. 3, and outputslog-likelihood ratio signal 810B.

Soft-in/soft-out decoder 811A takes log-likelihood ratio signal 810A asinput, performs decoding, and outputs a decoded log-likelihood ratio812A.

Similarly, soft-in/soft-out decoder 811B takes log-likelihood ratiosignal 810B as input, performs decoding, and outputs decodedlog-likelihood ratio 812B.

(Iterative Decoding (Iterative Detection), k Iterations)

The interleaver (813A) takes the k−1th decoded log-likelihood ratio 812Adecoded by the soft-in/soft-out decoder as input, performs interleaving,and outputs an interleaved log-likelihood ratio 814A. Here, theinterleaving pattern used by the interleaver (813A) is identical to thatof the interleaver (304A) from FIG. 3.

Another interleaver (813B) takes the k−1th decoded log-likelihood ratio812B decoded by the soft-in/soft-out decoder as input, performsinterleaving, and outputs interleaved log-likelihood ratio 814B. Here,the interleaving pattern used by the interleaver (813B) is identical tothat of the other interleaver (304B) from FIG. 3.

The inner MIMO detector 803 takes baseband signal 816X, transformedchannel estimation signal group 817X, baseband signal 816Y, transformedchannel estimation signal group 817Y, interleaved log-likelihood ratio814A, and interleaved log-likelihood ratio 814B as input. Here, basebandsignal 816X, transformed channel estimation signal group 817X, basebandsignal 816Y, and transformed channel estimation signal group 817Y areused instead of baseband signal 801X, channel estimation signal group802X, baseband signal 801Y, and channel estimation signal group 802Ybecause the latter cause delays due to the iterative decoding.

The iterative decoding operations of the inner MIMO detector 803 differfrom the initial detection operations thereof in that the interleavedlog-likelihood ratios 814A and 814B are used in signal processing forthe former. The inner MIMO detector 803 first calculates E(b0, b1, b2,b3, b4, b5, b6, b7) in the same manner as for initial detection. Inaddition, the coefficients corresponding to Math. 11 (formula 11) andMath. 32 (formula 32) are computed from the interleaved log-likelihoodratios 814A and 814B. The value of E(b0, b1, b2, b3, b4, b5, b6, b7) iscorrected using the coefficients so calculated to obtain E′(b0, b1, b2,b3, b4, b5, b6, b7), which is output as the signal 804.

The log-likelihood calculator 805A takes the signal 804 as input,calculates the log-likelihood of bits b0, b1, b2, and b3, and outputsthe log-likelihood signal 806A. Note that this log-likelihoodcalculation produces the log-likelihood of a bit being 1 and thelog-likelihood of a bit being 0. The calculation method is as shown inMath. 31 (formula 31) through Math. 35 (formula 35), and the details aregiven by Non-Patent Literature 2 and 3.

Similarly, log-likelihood calculator 805B takes the signal 804 as input,calculates the log-likelihood of bits b4, b5, b6, and b7, and outputslog-likelihood signal 806B. Operations performed by the deinterleaveronwards are similar to those performed for initial detection.

While FIG. 8 illustrates the configuration of the signal processor whenperforming iterative detection, this structure is not absolutelynecessary as good reception improvements are obtainable by iterativedetection alone. As long as the components needed for iterativedetection are present, the configuration need not include theinterleavers 813A and 813B. In such a case, the inner MIMO detector 803does not perform iterative detection.

The key point for the present Embodiment is the calculation ofH(t)×Y(t)×F. As shown in Non-Patent Literature 5 and the like, QRdecomposition may also be used to perform initial detection anditerative detection.

Also, as indicated by Non-Patent Literature 11, MMSE (MinimumMean-Square Error) and ZF (Zero-Forcing) linear operations may beperformed based on H(t)×Y(t)×F when performing initial detection.

FIG. 9 illustrates the configuration of a signal processor, unlike thatof FIG. 8, that serves as the signal processor for modulated signalstransmitted by the transmission device from FIG. 4. The point ofdifference from FIG. 8 is the number of soft-in/soft-out decoders. Asoft-in/soft-out decoder 901 takes the log-likelihood ratio signals 810Aand 810B as input, performs decoding, and outputs a decodedlog-likelihood ratio 902. A distributor 903 takes the decodedlog-likelihood ratio 902 as input for distribution. Otherwise, theoperations are identical to those explained for FIG. 8.

As described above, when a transmission device according to the presentEmbodiment using a MIMO system transmits a plurality of modulatedsignals from a plurality of antennas, changing the phase over time whilemultiplying by the precoding matrix so as to regularly change the phaseresults in improvements to data reception quality for a reception devicein a LOS environment, where direct waves are dominant, compared to aconventional spatial multiplexing MIMO system.

In the present Embodiment, and particularly in the configuration of thereception device, the number of antennas is limited and explanations aregiven accordingly. However, the Embodiment may also be applied to agreater number of antennas. In other words, the number of antennas inthe reception device does not affect the operations or advantageouseffects of the present Embodiment.

Also, although LDPC codes are described as a particular example, thepresent Embodiment is not limited in this manner, Furthermore, thedecoding method is not limited to the sum-product decoding example givenfor the soft-in/soft-out decoder. Other soft-in/soft-out decodingmethods, such as the BCJR algorithm, SOYA, and the Max-Log-Map algorithmmay also be used. Details are provided in Non-Patent Literature 6.

In addition, although the present Embodiment is described using asingle-carrier method, no limitation is intended in this regard. Thepresent Embodiment is also applicable to multi-carrier transmission.Accordingly, the present Embodiment may also be realized using, forexample, spread-spectrum communications, OFDM, SC-FDMA (Single CarrierFrequency-Division Multiple Access), SC-OFDM, wavelet OFDM as describedin Non-Patent Literature 7, and so on. Furthermore, in the presentEmbodiment, symbols other than data symbols, such as pilot symbols(preamble, unique word, and so on) or symbols transmitting controlinformation, may be arranged within the frame in any manner.

The following describes an example in which OFDM is used as amulti-carrier method.

FIG. 12 illustrates the configuration of a transmission device usingOFDM. In FIG. 12, components operating in the manner described for FIG.3 use identical reference numbers.

An OFDM-related processor 1201A takes weighted signal 309A as input,performs OFDM-related processing thereon, and outputs transmit signal1202A. Similarly, OFDM-related processor 1201B takes post-phase changesignal 309B as input, performs OFDM-related processing thereon, andoutputs transmit signal 1202B.

FIG. 13 illustrates a sample configuration of the OFDM-relatedprocessors 1201A and 1201B and onward from FIG. 12. Components 1301Athrough 1310A belong between 1201A and 312A from FIG. 12, whilecomponents 1301B through 1310B belong between 1201B and 312B.

Serial-to-parallel converter 1302A performs serial-to-parallelconversion on weighted signal 1301A (corresponding to weighted signal309A from FIG. 12) and outputs parallel signal 1303A.

Reorderer 1304A takes parallel signal 1303A as input, performsreordering thereof, and outputs reordered signal 1305A. Reordering isdescribed in detail later.

IFFT (Inverse Fast Fourier Transform) unit 1306A takes reordered signal1305A as input, applies an IFFT thereto, and outputs post-IFFT signal1307A.

Wireless unit 1308A takes post-IFFT signal 1307A as input, performsprocessing such as frequency conversion and amplification, thereon, andoutputs modulated signal 1309A. Modulated signal 1309A is then output asradio waves by antenna 1310A.

Serial-to-parallel converter 1302B performs serial-to-parallelconversion on weighted signal 1301B (corresponding to post-phase change309B from FIG. 12) and outputs parallel signal 1303B.

Reorderer 1304B takes parallel signal 1303B as input, performsreordering thereof, and outputs reordered signal 1305B. Reordering isdescribed in detail later.

IFFT unit 1306B takes reordered signal 1305B as input, applies an IFFTthereto, and outputs post-IFFT signal 1307B.

Wireless unit 1308B takes post-IFFT signal 1307B as input, performsprocessing such as frequency conversion and amplification thereon, andoutputs modulated signal 1309B. Modulated signal 1309B is then output asradio waves by antenna 1310A.

The transmission device from FIG. 3 does not use a multi-carriertransmission method. Thus, as shown in FIG. 6, a change of phase isperformed to achieve a period (cycle) of four and the post-phase changesymbols are arranged in the time domain. As shown in FIG. 12, whenmulti-carrier transmission, such as OFDM, is used, then, naturally,precoded post-phase change symbols may be arranged with respect to thetime domain as in FIG. 3, and this applies to each (sub-)carrier.However, for multi-carrier transmission, the arrangement may also be inthe frequency domain, or in both the frequency domain and the timedomain. The following describes these arrangements.

FIGS. 14A and 14B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13.The frequency axes are made up of (sub-)carriers 0 through 9. Themodulated signals z1 and z2 share common timestamps (timing) and use acommon frequency band. FIG. 14A illustrates a reordering method for thesymbols of modulated signal z1, while FIG. 14B illustrates a reorderingmethod for the symbols of modulated signal z2. With respect to thesymbols of weighted signal 1301A input to serial-to-parallel converter1302A, the assigned ordering is #0, #1, #2, #3, and so on. Here, giventhat the example deals with a period (cycle) of four, #0, #1, #2, and #3are equivalent to one period (cycle). Similarly, #4n, #4n+1, #4n+2, and#4n+3 (n being a non-zero positive integer) are also equivalent to oneperiod (cycle).

As shown in FIG. 14A, symbols #0, #1, #2, #3, and so on are arranged inorder, beginning at carrier 0. Symbols #0 through #9 are given timestamp$1, followed by symbols #10 through #19 which are given timestamp #2,and so on in a regular arrangement. Here, modulated signals z1 and z2are complex signals.

Similarly, with respect to the symbols of weighted signal 1301B input toserial-to-parallel converter 1302B, the assigned ordering is #0, #1, #2,#3, and so on. Here, given that the example deals with a period (cycle)of four, a different change in phase is applied to each of #0, #1, #2,and #3, which are equivalent to one period (cycle). Similarly, adifferent change in phase is applied to each of #4n, #4n+1, #4n+2, and#4n+3 (n being a non-zero positive integer), which are also equivalentto one period (cycle).

As shown in FIG. 14B, symbols #0, #1, #2, #3, and so on are arranged inorder, beginning at carrier 0. Symbols #0 through #9 are given timestamp$1, followed by symbols #10 through #19 which are given timestamp $2,and so on in a regular arrangement.

The symbol group 1402 shown in FIG. 14B corresponds to one period(cycle) of symbols when the phase changing method of FIG. 6 is used.Symbol #0 is the symbol obtained by using the phase at timestamp u inFIG. 6, symbol #1 is the symbol obtained by using the phase at timestampu+1 in FIG. 6, symbol #2 is the symbol obtained by using the phase attimestamp u+2 in FIG. 6, and symbol #3 is the symbol obtained by usingthe phase at timestamp u+3 in FIG. 6. Accordingly, for any symbol #x,symbol #x is the symbol obtained by using the phase at timestamp u inFIG. 6 when x mod 4 equals 0 (i.e., when the remainder of x divided by 4is 0, mod being the modulo operator), symbol #x is the symbol obtainedby using the phase at timestamp u+1 in FIG. 6 when x mod 4 equals 1,symbol #x is the symbol obtained by using the phase at timestamp u+2 inFIG. 6 when x mod 4 equals 2, and symbol #x is the symbol obtained byusing the phase at timestamp u+3 in FIG. 6 when x mod 4 equals 3.

In the present Embodiment, modulated signal z1 shown in FIG. 14A has notundergone a change of phase.

As such, when using a multi-carrier transmission method such as OFDM,and unlike single carrier transmission, symbols can be arranged in thefrequency domain. Of course, the symbol arrangement method is notlimited to those illustrated by FIGS. 14A and 14B. Further examples areshown in FIGS. 15A, 15B, 16A, and 16B.

FIGS. 15A and 15B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from that of FIGS. 14A and 14B. FIG. 15A illustrates areordering method for the symbols of modulated signal z1, while FIG. 15Billustrates a reordering method for the symbols of modulated signal z2.FIGS. 15A and 15B differ from FIGS. 14A and 14B in the reordering methodapplied to the symbols of modulated signal z1 and the symbols ofmodulated signal z2. In FIG. 15B, symbols #0 through #5 are arranged atcarriers 4 through 9, symbols #6 though #9 are arranged at carriers 0through 3, and this arrangement is repeated for symbols #10 through #19.Here, as in FIG. 14B, symbol group 1502 shown in FIG. 15B corresponds toone period (cycle) of symbols when the phase changing method of FIG. 6is used.

FIGS. 16A and 16B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from that of FIGS. 14A and 14B. FIG. 16A illustrates areordering method for the symbols of modulated signal z1, while FIG. 16Billustrates a reordering method for the symbols of modulated signal z2.FIGS. 16A and 16B differ from FIGS. 14A and 14B in that, while FIGS. 14Aand 14B showed symbols arranged at sequential carriers, FIGS. 16A and16B do not arrange the symbols at sequential carriers. Obviously, forFIGS. 16A and 16B, different reordering methods may be applied to thesymbols of modulated signal z1 and to the symbols of modulated signal z2as in FIGS. 15A and 15B.

FIGS. 17A and 17B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from those of FIGS. 14A through 16B. FIG. 17A illustrates areordering method for the symbols of modulated signal z1 while FIG. 17Billustrates a reordering method for the symbols of modulated signal z2.While FIGS. 14A through 16B show symbols arranged with respect to thefrequency axis, FIGS. 17A and 17B use the frequency and time axestogether in a single arrangement.

While FIG. 6 describes an example where the change of phase is performedin a four slot period (cycle), the following example describes an eightslot period (cycle). In FIGS. 17A and 17B, the symbol group 1702 isequivalent to one period (cycle) of symbols when the phase changingscheme is used (i.e., to eight symbols) such that symbol #0 is thesymbol obtained by using the phase at timestamp u, symbol #1 is thesymbol obtained by using the phase at timestamp u+1, symbol #2 is thesymbol obtained by using the phase at timestamp u+2, symbol #3 is thesymbol obtained by using the phase at timestamp u+3, symbol #4 is thesymbol obtained by using the phase at timestamp u+4, symbol #5 is thesymbol obtained by using the phase at timestamp u+5, symbol #6 is thesymbol obtained by using the phase at timestamp u+6, and symbol #7 isthe symbol obtained by using the phase at timestamp u+7. Accordingly,for any symbol #x, symbol #x is the symbol obtained by using the phaseat timestamp u when x mod 8 equals 0, symbol #x is the symbol obtainedby using the phase at timestamp u+1 when x mod 8 equals 1, symbol #x isthe symbol obtained by using the phase at timestamp u+2 when x mod 8equals 2, symbol #x is the symbol obtained by using the phase attimestamp u+3 when x mod 8 equals 3, symbol #x is the symbol obtained byusing the phase at timestamp u+4 when x mod 8 equals 4, symbol #x is thesymbol obtained by using the phase at timestamp u+5 when x mod 8 equals5, symbol #x is the symbol obtained by using the phase at timestamp u+6when x mod 8 equals 6, and symbol #x is the symbol obtained by using thephase at timestamp u+7 when x mod 8 equals 7. In FIGS. 17A and 17B fourslots along the time axis and two slots along the frequency axis areused for a total of 4×2=8 slots, in which one period (cycle) of symbolsis arranged. Here, given m×n symbols per period (cycle) (i.e., m×ndifferent phases are available for multiplication), then n slots(carriers) in the frequency domain and m slots in the time domain shouldbe used to arrange the symbols of each period (cycle), such that m>n.This is because the phase of direct waves fluctuates slowly in the timedomain relative to the frequency domain. Accordingly, the presentEmbodiment performs a regular change of phase that reduces the influenceof steady direct waves. Thus, the phase changing period (cycle) shouldpreferably reduce direct wave fluctuations. Accordingly, m should begreater than n. Taking the above into consideration, using the time andfrequency domains together for reordering, as shown in FIGS. 17A and17B, is preferable to using either of the frequency domain or the timedomain alone due to the strong probability of the direct waves becomingregular. As a result, the effects of the present invention are moreeasily obtained. However, reordering in the frequency domain may lead todiversity gain due the fact that frequency-domain fluctuations areabrupt. As such, using the frequency and time domains together forreordering is not always ideal.

FIGS. 18A and 18B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from that of FIGS. 17A and 17B. FIG. 18A illustrates areordering method for the symbols of modulated signal z1, while FIG. 18Billustrates a reordering method for the symbols of modulated signal z2.Much like FIGS. 17A and 17B, FIGS. 18A and 18B illustrate the use of thetime and frequency axes, together. However, in contrast to FIGS. 17A and17B, where the frequency axis is prioritized and the time axis is usedfor secondary symbol arrangement, FIGS. 18A and 18B prioritize the rimeaxis and use the frequency axis for secondary symbol arrangement. InFIG. 18B, symbol group 1802 corresponds to one period (cycle) of symbolswhen the phase changing method is used.

In FIGS. 17A, 17B, 18A, and 18B, the reordering method applied to thesymbols of modulated signal z1 and the symbols of modulated signal z2may be identical or may differ as like in FIGS. 15A and 15B. Eitherapproach allows good reception quality to be obtained. Also, in FIGS.17A, 17B, 18A, and 18B, the symbols may be arranged non-sequentially asin FIGS. 16A and 16B. Either approach allows good reception quality tobe obtained.

FIG. 22 indicates frequency on the horizontal axis and time on thevertical axis thereof, and illustrates an example of a symbol reorderingmethod used by the reorderers 1301A and 1301B from FIG. 13 that differsfrom the above. FIG. 22 illustrates a regular phase changing methodusing four slots, similar to timestamps u through u+3 from FIG. 6. Thecharacteristic feature of FIG. 22 is that, although the symbols arereordered with respect the frequency domain, when read along the timeaxis, a periodic shift of n (n=1 in the example of FIG. 22) symbols isapparent. The frequency-domain symbol group 2210 in FIG. 22 indicatesfour symbols to which the change of phase is applied at timestamps uthrough u+3 from FIG. 6.

Here, symbol #0 is obtained through a change of phase at timestamp u,symbol #1 is obtained through a change of phase at timestamp u+1, symbol#2 is obtained through a change of phase at timestamp u+2, and symbol #3is obtained through a change of phase at timestamp u+3.

Similarly, for frequency-domain symbol group 2220, symbol #4 is obtainedthrough a change of phase at timestamp u, symbol #5 is obtained througha change of phase at timestamp u+1, symbol #6 is obtained through achange of phase at timestamp u+2, and symbol #7 is obtained through achange of phase at timestamp u+3.

The above-described change of phase is applied to the symbol attimestamp $1. However, in order to apply periodic shifting with respectto the time domain, the following change of phases are applied to symbolgroups 2201, 2202, 2203, and 2204.

For time-domain symbol group 2201, symbol #0 is obtained through achange of phase at timestamp u, symbol #9 is obtained through a changeof phase at timestamp u+1, symbol #18 is obtained through a change ofphase at timestamp u+2, and symbol #27 is obtained through a change ofphase at timestamp u+3.

For time-domain symbol group 2202, symbol #28 is obtained through achange of phase at timestamp u, symbol #1 is obtained through a changeof phase at timestamp u+1, symbol #10 is obtained through a change ofphase at timestamp u+2, and symbol #19 is obtained through a change ofphase at timestamp u+3.

For time-domain symbol group 2203, symbol #20 is obtained through achange of phase at timestamp u, symbol #29 is obtained through a changeof phase at timestamp u+1, symbol #2 is obtained through a change ofphase at timestamp u+2, and symbol #11 is obtained through a change ofphase at timestamp u+3.

For time-domain symbol group 2204, symbol #12 is obtained through achange of phase at timestamp u, symbol #21 is obtained through a changeof phase at timestamp u+1, symbol #30 is obtained through a change ofphase at timestamp u+2, and symbol #3 is obtained through a change ofphase at timestamp u+3.

The characteristic feature of FIG. 22 is seen in that, taking symbol #11as an example, the two neighbouring symbols thereof having the sametimestamp in the frequency domain (#10 and #12) are both symbols changedusing a different phase than symbol #11, and the two neighbouringsymbols thereof having the same carrier in the time domain (#2 and #20)are both symbols changed using a different phase than symbol #11. Thisholds not only for symbol #11, but also for any symbol having twoneighbouring symbols in the frequency domain and the time domain.Accordingly, the change of phase is effectively carried out. This ishighly likely to improve data reception quality as influence fromregularizing direct waves is less prone to reception.

Although FIG. 22 illustrates an example in which n=1, the invention isnot limited in this manner. The same may be applied to a case in whichn=3. Furthermore, although FIG. 22 illustrates the realization of theabove-described effects by arranging the symbols in the frequency domainand advancing in the time domain so as to achieve the characteristiceffect of imparting a periodic shift to the symbol arrangement order,the symbols may also be randomly (or regularly) arranged to the sameeffect.

Embodiment 2

In Embodiment 1, described above, phase changing is applied to aweighted (precoded with a fixed precoding matrix) signal z(t). Thefollowing Embodiments describe various phase changing methods by whichthe effects of Embodiment 1 may be obtained.

In the above-described Embodiment, as shown in FIGS. 3 and 6, phasechanger 317B is configured to perform a change of phase on only one ofthe signals output by the weighting unit 600.

However, phase changing may also be applied before precoding isperformed by the weighting unit 600. In addition to the componentsillustrated in FIG. 6, the transmission device may also feature theweighting unit 600 before the phase changer 317B, as shown in FIG. 25.

In such circumstances, the following configuration is possible. Thephase changer 317B performs a regular change of phase with respect tobaseband signal s2(t), on which mapping has been performed according toa selected modulation scheme, and outputs s2′(t)=s2(t) y(t) (where y(t)varies over time t). The weighting unit 600 executes precoding on s2′t,outputs z2(t)=W2s2′(t) (see Math. 42 (formula 42)) and the result isthen transmitted.

Alternatively, phase changing may be performed on both modulated signalss1(t) and s2(t). As such, the transmission device is configured so as toinclude a phase changer taking both signals output by the weighting unit600, as shown in FIG. 26.

Like phase changer 317B, phase changer 317A performs regular a regularchange of phase on the signal input thereto, and as such changes thephase of signal z1′(t) precoded by the weighting unit. Post-phase changesignal z1(t) is then output to a transmitter.

However, the phase changing rate applied by the phase changers 317A and317B varies simultaneously in order to perform the phase changing shownin FIG. 26. (The following describes a non-limiting example of the phasechanging method.) For timestamp u, phase changer 317A from FIG. 26performs the change of phase such that z1(t)=y1(t)z1′(t), while phasechanger 317B performs the change of phase such that z2(t)=y2(t)z2′(t).For example, as shown in FIG. 26, for timestamp u, y₁(u)=e^(j0) andy₂(u)=e^(−jπ/2), for timestamp u+1, y₁(u+1)=e^(jπ/4) andy₂(u+1)=e^(−j3π/4), and for timestamp u+k, y₁(u+k)=e^(jkπ/4) andy₂(u+k)=e^(j(k3π/4−π/2)). Here, the regular phase changing period(cycle) may be the same for both phase changers 317A and 317B, or mayvary for each.

Also, as described above, a change of phase may be performed beforeprecoding is performed by the weighting unit. In such a case, thetransmission device should be configured as illustrated in FIG. 27rather than as illustrated in FIG. 26.

When a change of phase is carried out on both modulated signals, each ofthe transmit signals is, for example, control information that includesinformation about the phase changing pattern. By obtaining the controlinformation, the reception device knows the phase changing method bywhich the transmission device regularly varies the change, i.e., thephase changing pattern, and is thus able to demodulate (decode) thesignals correctly.

Next, variants of the sample configurations shown in FIGS. 6 and 25 aredescribed with reference to FIGS. 28 and 29. FIG. 28 differs from FIG. 6in the inclusion of phase change ON/OFF information 2800 and in that thechange of phase is performed on only one of z1′(t) and z2′(t) (i.e.,performed on one of z1′(t) and z2′(t), which have identical timestampsor a common frequency). Accordingly, in order to perform the change ofphase on one of z1′(t) and z2′(t), the phase changers 317A and 317Bshown in FIG. 28 may each be ON, and performing the change of phase, orOFF, and not performing the change of phase. The phase change ON/OFFinformation 2800 is control information therefor. The phase changeON/OFF information 2800 is output by the signal processing methodinformation generator 314 shown in FIG. 3.

Phase changer 317A of FIG. 28 changes the phase to producez1(t)=y₁(t)z1′(t), while phase changer 317B changes the phase to producez2(t)=y₂(t)z2′(t).

Here, a change of phase having a period (cycle) of four is, for example,applied to z1′(t). (Meanwhile, the phase of z2′(t) is not changed.)Accordingly, for timestamp u, y₁(u)=e^(j0) and y₂(u)=1, for timestampu+1, y₁(u+1)=e^(jπ/2) and y₂(u+1)=1, for timestamp u+2, y₁(u+2)=e^(jπ)and y₂(u+2)=1, and for timestamp u+3, y₁(u+³)=e^(j3π/2) and y₂(u+3)=1.

Next, a change of phase having a period (cycle) of four is, for example,applied to z2′(t). (Meanwhile, the phase of z1′(t) is not changed.)Accordingly, for timestamp u+4, y₁(u+4)=1 and y₂(u+4)=e^(j0), fortimestamp u+5, y₁(u+5)=1 and y₂(u+5)=e^(jπ/2), for timestamp u+6,y₁(u+6)=1 and y₂(u+6)=e^(jπ), and for timestamp u+7, y₁(u+7)=1 andy₂(u+7)=e^(j3π/2).

Accordingly, given the above examples.

for any timestamp 8k, y₁(8k)=e^(j0) and y₂(8k)=1,

for any timestamp 8k+1, y₁(8k+1)=e^(jπ/2) and y₂(8k+1)=1,

for any timestamp 8k+2, y₁(8k+2)=e^(jπ) and y₂(8k+2)=1,

for any timestamp 8k+3, y₁(8k+3)=e^(j3π/2) and y₂(8k+3)=1,

for any timestamp 8k+4, y₁(8k+4)=1 and y₂(8k+4)=e^(j0),

for any timestamp 8k+5, y₁(8k+3)=1 and y₂(8k+5)=e^(jπ/2),

for any timestamp 8k+6, y₁(8k+6)=1 and y₂(8k+6)=e^(jπ), and

for any timestamp 8k+7, y₁(8k+7)=1 and y₂(8k+7)=e^(j3π/2).

As described above, there are two intervals, one where the change ofphase is performed on z1′(t) only, and one where the change of phase isperformed on z2′(t) only. Furthermore, the two intervals form a phasechanging period (cycle). While the above explanation describes theinterval where the change of phase is performed on z1′(t) only and theinterval where the change of phase is performed on z2′(t) only as beingequal, no limitation is intended in this manner. The two intervals mayalso differ. In addition, while the above explanation describesperforming a change of phase having a period (cycle) of four on z1′(t)only and then performing a change of phase having a period (cycle) offour on z2′(t) only, no limitation is intended in this manner. Thechanges of phase may be performed on z1′(t) and on z2′(t) in any order(e.g., the change of phase may alternate between being performed onz1′(t) and on z2′(t), or may be performed in random order).

Phase changer 317A of FIG. 29 changes the phase to produce s1′(t)=y₁(t)s1(t), while phase changer 317B changes the phase to produces2′(t)=y₂(t) s2(t).

Here, a change of phase having a period (cycle) of four is, for example,applied to s1(t). (Meanwhile, s2(t) remains unchanged). Accordingly, fortimestamp u, y₁(u)=e^(j0) and y₂(u)=1, for timestamp u+1,y₁(u+1)=e^(jπ/2) and y₂(u+1)=1, for timestamp u+2, y₁(u+2)=e^(jπ) andy₂(u+2)=1, and for timestamp u+3, y₁(u+3)=e^(j3π/2) and y₂(u+3)=1.

Next, a change of phase having a period (cycle) of four is, for example,applied to s2(t). (Meanwhile, s1(t) remains unchanged). Accordingly, fortimestamp u+4, y₁(u+4)=1 and y₂(u+4)=e^(j0), for timestamp u+5,y₁(u+5)=1 and y₂(u+5)=e^(jπ/2), for timestamp u+6, y₁(u+6)=1 andy₂(u+6)=e^(jπ), and for timestamp u+7, y₁(u+7)=1 and y₂(u+7)=e^(j3π/2).

Accordingly, given the above examples,

for any timestamp 8k, y₁(8k)=e^(j0) and y₂(8k)=1,

for any timestamp 8k+1, y_(i)(8k+1)=e^(jπ/2) and y₂(8k+1)=1,

for any timestamp 8k+2, y₁(8k+2)=e^(jπ) and y₂(8k+2)=1,

for any timestamp 8k+3, y₁(8k+3)=e^(j3π/2) and y₂(8k+3)=1,

for any timestamp 8k+4, y₁(8k+4)=1 and y₂(8k+4)=e^(j0),

for any timestamp 8k+5, y₁(8k+5)=1 and y₂(8k+5)=e^(jπ/2),

for any timestamp 8k+6, y₁(8k+6)=1 and y₂(8k+6)=e^(jπ), and

for any timestamp 8k+7, y₁(8k+7)=1 and y₂(8k+7)=e^(j3π/2).

As described above, there are two intervals, one where the change ofphase is performed on s1(t) only, and one where the change of phase isperformed on s2(t) only. Furthermore, the two intervals form a phasechanging period (cycle). Although the above explanation describes theinterval where the change of phase is performed on s1(t) only and theinterval where the change of phase is performed on s2(t) only as beingequal, no limitation is intended in this manner. The two intervals mayalso differ. In addition, while the above explanation describesperforming the change of phase having a period (cycle) of four on s1(t)only and then performing the change of phase having a period (cycle) offour on s2(t) only, no limitation is intended in this manner. Thechanges of phase may be performed on s1(t) and on s2(t) in any order(e.g., may alternate between being performed on s1(t) and on s2(t), ormay be performed in random order).

Accordingly, the reception conditions under which the reception devicereceives each transmit signal z1(t) and z2(t) are equalized. Byperiodically switching the phase of the symbols in the received signalsz1(t) and z2(t), the ability of the error corrected codes to correcterrors may be improved, thus ameliorating received signal quality in theLOS environment.

Accordingly, Embodiment 2 as described above is able to produce the sameresults as the previously described Embodiment 1.

Although the present Embodiment used a single-carrier method, i.e., timedomain phase changing, as an example, no limitation is intended in thisregard. The same effects are also achievable using multi-carriertransmission. Accordingly, the present Embodiment may also be realizedusing, for example, spread-spectrum communications, OFDM, SC-FDMA(Single Carrier Frequency-Division Multiple Access), SC-OFDM, waveletOFDM as described in Non-Patent Literature 7, and so on. As previouslydescribed, while the present Embodiment explains the change of phase aschanging the phase with respect to the time domain t, the phase mayalternatively be changed with respect to the frequency domain asdescribed in Embodiment 1. That is, considering the phase changingmethod in the time domain t described in the present Embodiment andreplacing t with f (f being the ((sub-) carrier) frequency) leads to achange of phase applicable to the frequency domain. Also, as explainedabove for Embodiment 1, the phase changing method of the presentEmbodiment is also applicable to a change of phase with respect to boththe time domain and the frequency domain.

Accordingly, although FIGS. 6, 25, 26, and 27 illustrate changes ofphase in the time domain, replacing time t with carrier f in each ofFIGS. 6, 25, 26, and 27 corresponds to a change of phase in thefrequency domain. In other words, replacing (t) with (t, f) where t istime and f is frequency corresponds to performing the change of phase ontime-frequency blocks.

Furthermore, in the present Embodiment, symbols other than data symbols,such as pilot symbols (preamble, unique word, etc) or symbolstransmitting control information, may be arranged within the frame inany manner.

Embodiment 3

Embodiments 1 and 2, described above, discuss regular changes of phase.Embodiment 3 describes a method of allowing the reception device toobtain good received signal quality for data, regardless of thereception device arrangement, by considering the location of thereception device with respect to the transmission device.

Embodiment 3 concerns the symbol arrangement within signals obtainedthrough a change of phase.

FIG. 31 illustrates an example of frame configuration for a portion ofthe symbols within a signal in the time-frequency domains, given atransmission method where a regular change of phase is performed for amulti-carrier method such as OFDM.

First, an example is explained in which the change of phase is performedone of two baseband signals, precoded as explained in Embodiment 1 (seeFIG. 6).

(Although FIG. 6 illustrates a change of phase in the time domain,switching time t with carrier f in FIG. 6 corresponds to a change ofphase in the frequency domain. In other words, replacing (t) with (t, f)where t is time and f is frequency corresponds to performing phasechanges on time-frequency blocks.)

FIG. 31 illustrates the frame configuration of modulated signal z2′,which is input to phase changer 317B from FIG. 12. Each squarerepresents one symbol (although both signals s1 and s2 are included forprecoding purposes, depending on the precoding matrix, only one ofsignals s1 and s2 may be used).

Consider symbol 3100 at carrier 2 and timestamp $2 of FIG. 31. Thecarrier here described may alternatively be termed a sub-carrier.

Within carrier 2, there is a very strong correlation between the channelconditions for symbol 3100A at carrier 2, timestamp $2 and the channelconditions for the time domain nearest-neighbour symbols to timestamp$2, i.e., symbol 3013 at timestamp $1 and symbol 3101 at timestamp $3within carrier 2.

Similarly, for timestamp $2, there is a very strong correlation betweenthe channel conditions for symbol 3100 at carrier 2, timestamp $2 andthe channel conditions for the frequency-domain nearest-neighboursymbols to carrier 2, i.e., symbol 3104 at carrier 1, timestamp $2 andsymbol 3104 at timestamp $2, carrier 3.

As described above, there is a very strong correlation between thechannel conditions for symbol 3100 and the channel conditions for eachsymbol 3101, 3102, 3103, and 3104.

The present description considers N different phases (N being aninteger, N≧2) for multiplication in a transmission method where thephase is regularly changed. The symbols illustrated in FIG. 31 areindicated as e^(j0), for example. This signifies that this symbol issignal z2′ from FIG. 6 having undergone a change in phase throughmultiplication by e^(j0). That is, the values indicated in FIG. 31 foreach of the symbols are the values of y(t) from Math. 42 (formula 42),which are also the values of z2(t)=y₂(t)z2′(t) described in Embodiment2.

The present Embodiment takes advantage of the high correlation inchannel conditions existing between neighbouring symbols in thefrequency domain and/or neighbouring symbols in the time domain in asymbol arrangement enabling high data reception quality to be obtainedby the reception device receiving the phase-changed symbols.

In order to achieve this high data reception quality, conditions #1 and#2 are necessary.

(Condition #1)

As shown in FIG. 6, for a transmission method involving a regular changeof phase performed on precoded baseband signal z2′ using multi-carriertransmission such as OFDM, time X, carrier Y is a symbol fortransmitting data (hereinafter, data symbol), neighbouring symbols inthe time domain, i.e., at time X−1, carrier Y and at time X+1, carrier Yare also data symbols, and a different change of phase should beperformed on precoded baseband signal z2′ corresponding to each of thesethree data symbols, i.e., on precoded baseband signal z2′ at time X,carrier Y, at time X−1, carrier Y and at time X+1, carrier Y.

(Condition #2)

As shown in FIG. 6, for a transmission method involving a regular changeof phase performed on precoded baseband signal z2′ using multi-carriertransmission such as OFDM, time X, carrier Y is a data symbol,neighbouring symbols in the frequency domain, i.e., at time X, carrierY−1 and at time X, carrier Y+1 are also data symbols, and a differentchange of phase should be performed on precoded baseband signal z2′corresponding to each of these three data symbols, i.e., on precodedbaseband signal z2′ at time X, carrier Y, at time X, carrier Y−1 and attime X, carrier Y+1.

Ideally, data symbols satisfying Condition #1 should be present.Similarly, data symbols satisfying Condition #2 should be present.

The reasons supporting Conditions #1 and #2 are as follows.

A very strong correlation exists between the channel conditions of givensymbol of a transmit signal (hereinafter, symbol A) and the channelconditions of the symbols neighbouring symbol A in the time domain, asdescribed above.

Accordingly, when three neighbouring symbols in the time domain eachhave different phases, then despite reception quality degradation in theLOS environment (poor signal quality caused by degradation in conditionsdue to phase relations despite high signal quality in terms of SNR) forsymbol A, the two remaining symbols neighbouring symbol A are highlylikely to provide good reception quality. As a result, good receivedsignal quality is achievable after error correction and decoding.

Similarly, a very strong correlation exists between the channelconditions of given symbol of a transmit signal (hereinafter, symbol A)and the channel conditions of the symbols neighbouring symbol A in thefrequency domain, as described above.

Accordingly, when three neighbouring symbols in the frequency domaineach have different phases, then despite reception quality degradationin the LOS environment (poor signal quality caused by degradation inconditions due to direct wave phase relationships despite high signalquality in terms of SNR) for symbol A, the two remaining symbolsneighbouring symbol A are highly likely to provide good receptionquality. As a result, good received signal quality is achievable aftererror correction and decoding.

Combining Conditions #1 and #2, ever greater data reception quality islikely achievable for the reception device. Accordingly, the followingCondition #3 can be derived.

(Condition #3)

As shown in FIG. 6, for a transmission method involving a regular changeof phase performed on precoded baseband signal z2′ using multi-carriertransmission such as OFDM, time X, carrier Y is a data symbol,neighbouring symbols in the time domain, i.e., at time X−1, carrier Yand at time X+1, carrier Y are also data symbols, and neighbouringsymbols in the frequency domain, i.e., at time X, carrier Y−1 and attime X, carrier Y+1 are also data symbols, and a different change inphase is performed on precoded baseband signal z2′ corresponding to eachof these five data symbols, i.e., on precoded baseband signal z2′ attime X, carrier Y, at time X, carrier Y−1, at time X, carrier Y+1, at atime X−1, carrier Y, and at time X+1, carrier Y.

Here, the different changes in phase are as follows. Phase changes aredefined from 0 radians to 2π radians. For example, for time X, carrierY, a phase change of e^(jθX,Y) is applied to precoded baseband signalz2′ from FIG. 6, for time X−1, carrier Y, a phase change of e^(jθX−1,Y)is applied to precoded baseband signal z2′ from FIG. 6, for time X+1,carrier Y, a phase change of e^(jθX+1,Y) is applied to precoded basebandsignal z2′ from FIG. 6, such that 0≦θ_(X,Y)<2π, 0≦θ_(X−1,Y)<2π, and0≦θ_(X+1,Y)<2π, all units being in radians. Accordingly, for Condition#1, it follows that θ_(X,Y)≠θ_(X−1,Y), θ_(X,Y)≠θ_(X+1,Y), and thatθ_(X−1,Y)≠θ_(X+1,Y). Similarly, for Condition #2, it follows thatθ_(X,Y)≠θ_(X,Y−1), θ_(X,Y)≠θ_(X,Y+1), and that θ_(X,Y−1)≠θ_(X,Y+1). And,for Condition #3, it follows that θ_(X,Y)≠θ_(X−1,Y), θ_(X,Y)≠θ_(X+1,Y),θ_(X,Y)≠θ_(X,Y−1), θ_(X,Y)≠θ_(X,Y−1), θ_(X−1,Y)≠θ_(X+1,Y),θ_(X−1,Y)≠θ_(X,Y−1), θ_(X−1,Y)≠θ_(X+1,Y), θ_(X+1,Y)≠θ_(X−1,Y),θ_(X+1,Y)≠θ_(X,Y+1), and that θ_(X,Y−1)≠θ_(X,Y+1).

Ideally, data symbols satisfying Condition #3 should be present.

FIG. 31 illustrates an example of Condition #3 where symbol Acorresponds to symbol 3100. The symbols are arranged such that the phaseby which precoded baseband signal z2′ from FIG. 6 is multiplied differsfor symbol 3100, for both neighbouring symbols thereof in the timedomain 3101 and 3102, and for both neighbouring symbols thereof in thefrequency domain 3102 and 3104. Accordingly, despite received signalquality degradation of symbol 3100 for the receiver, good signal qualityis highly likely for the neighbouring signals, thus guaranteeing goodsignal quality after error correction.

FIG. 32 illustrates a symbol arrangement obtained through phase changesunder these conditions.

As evident from FIG. 32, with respect to any data symbol, a differentchange in phase is applied to each neighbouring symbol in the timedomain and in the frequency domain. As such, the ability of thereception device to correct errors may be improved.

In other words, in FIG. 32, when all neighbouring symbols in the timedomain are data symbols, Condition #1 is satisfied for all Xs and allYs.

Similarly, in FIG. 32, when all neighbouring symbols in the frequencydomain are data symbols, Condition #2 is satisfied for all Xs and allYs.

Similarly, in FIG. 32, when all neighbouring symbols in the frequencydomain are data symbols and all neighbouring symbols in the time domainare data symbols, Condition #3 is satisfied for all Xs and all Ys.

The following describes an example in which a change of phase isperformed on two precoded baseband signals, as explained in Embodiment 2(see FIG. 26).

When a change of phase is performed on precoded baseband signal z1′ andprecoded baseband signal z2′ as shown in FIG. 26, several phase changingmethods are possible. The details thereof are explained below.

Scheme 1 involves a change in phase of precoded baseband signal z2′ asdescribed above, to achieve the change in phase illustrated by FIG. 32.In FIG. 32, a change of phase having a period (cycle) of ten is appliedto precoded baseband signal z2′. However, as described above, in orderto satisfy Conditions #1, #2, and #3, the change in phase applied toprecoded baseband signal z2′ at each (sub-)carrier varies over time.(Although such changes are applied in FIG. 32 with a period (cycle) often, other phase changing methods are also possible.) Then, as shown inFIG. 33, the change in phase performed on precoded baseband signal z1′produces a constant value that is one-tenth of that of the change inphase performed on precoded baseband signal z2′. In FIG. 33, for aperiod (cycle) (of change in phase performed on precoded baseband signalz2′) including timestamp $1, the value of the change in phase performedon precoded baseband signal z1′ is e^(j0). Then, for the next period(cycle) (of change in phase performed on precoded baseband signal z2′)including timestamp $2, the value of the change in phase performed onprecoded baseband signal z1′ is e^(jπ/9), and so on.

The symbols illustrated in FIG. 33 are indicated as e^(j0), for example.This signifies that this symbol is signal z1′ from FIG. 26 to which achange in phase has been applied through multiplication by e^(j0). Thatis, the values indicated in FIG. 33 for each of the symbols are thevalues of z1(t)=y₁(t)z1′(t) described in Embodiment 2 for y₁(t).

As shown in FIG. 33, the change in phase performed on precoded basebandsignal z1′ produces a constant value that is one-tenth that of thechange in phase performed on precoded baseband signal z2′ such that thepost-phase change value varies with the number of each period (cycle).(As described above, in FIG. 33, the value is e^(j0) for the firstperiod (cycle), e^(jπ/9) for the second period (cycle), and so on.)

As described above, the change in phase performed on precoded basebandsignal z2′ has a period (cycle) of ten, but the period (cycle) can beeffectively made greater than ten by taking the change in phase appliedto precoded baseband signal z1′ and to precoded baseband signal z2′ intoconsideration. Accordingly, data reception quality may be improved forthe reception device.

Scheme 2 involves a change in phase of precoded baseband signal z2′ asdescribed above, to achieve the change in phase illustrated by FIG. 32.In FIG. 32, a change of phase having a period (cycle) of ten is appliedto precoded baseband signal z2′. However, as described above, in orderto satisfy Conditions #1, #2, and #3, the change in phase applied toprecoded baseband signal z2′ at each (sub-)carrier varies over time.(Although such changes are applied in FIG. 32 with a period (cycle) often, other phase changing methods are also possible.) Then, as shown inFIG. 30, the change in phase performed on precoded baseband signal z1′differs from that performed on precoded baseband signal z2′ in having aperiod (cycle) of three rather than ten.

The symbols illustrated in FIG. 30 are indicated as e^(j0), for example.This signifies that this symbol is signal z1′ from FIG. 26 to which achange in phase has been applied through multiplication by e^(j0). Thatis, the values indicated in FIG. 30 for each of the symbols are thevalues of z1(t)=y₁(t)z1′(t) described in Embodiment 2 for y₁(t).

As described above, the change in phase performed on precoded basebandsignal z2′ has a period (cycle) of ten, but by taking the changes inphase applied to precoded baseband signal z1′ and precoded basebandsignal z2′ into consideration, the period (cycle) can be effectivelymade equivalent to 30 for both precoded baseband signals z1′ and z2′.Accordingly, data reception quality may be improved for the receptiondevice. An effective way of applying method 2 is to perform a change inphase on precoded baseband signal z1′ with a period (cycle) of N andperform a change in phase on precoded baseband signal z2′ with a period(cycle) of M such that N and M are coprime. As such, by taking bothprecoded baseband signals z1′ and z2′ into consideration, a period(cycle) of N×M is easily achievable, effectively making the period(cycle) greater when N and M are coprime.

The above describes an example of the phase changing method pertainingto Embodiment 3. The present invention is not limited in this manner. Asexplained for Embodiments 1 and 2, a change in phase may be performedwith respect the frequency domain or the time domain, or ontime-frequency blocks. Similar improvement to the data reception qualitycan be obtained for the reception device in all cases.

The same also applies to frames having a configuration other than thatdescribed above, where pilot symbols (SP symbols) and symbolstransmitting control information are inserted among the data symbols.The details of the change in phase in such circumstances are as follows.

FIGS. 47A and 47B illustrate the frame configuration of modulatedsignals (precoded baseband signals) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 47A illustrates the frame configuration ofmodulated signal (precoded baseband signal) z1 or z1′ while FIG. 47Billustrates the frame configuration of modulated signal (precodedbaseband signal) z2′. In FIGS. 47A and 47B, 4701 marks pilot symbolswhile 4702 marks data symbols. The data symbols 4702 are symbols onwhich precoding or precoding and a change in phase have been performed.

FIGS. 47A and 47B, like FIG. 6, indicate the arrangement of symbols whena change in phase is applied to precoded baseband signal z2′ (while nochange of phase is performed on precoded baseband signal z1). (AlthoughFIG. 6 illustrates a change in phase with respect to the time domain,switching time t with carrier f in FIG. 6 corresponds to a change inphase with respect to the frequency domain. In other words, replacing(t) with (t, f) where t is time and f is frequency corresponds toperforming a change of phase on time-frequency blocks.) Accordingly, thenumerical values indicated in FIGS. 47A and 47B for each of the symbolsare the values of precoded baseband signal z2′ after a change of phaseis performed. No values are given for the symbols of precoded basebandsignal z1′ (z1) as no change of phase is performed thereon.

The key point of FIGS. 47A and 47B is that a change of phase isperformed on the data symbols of precoded baseband signal z2′, i.e., onprecoded symbols. (The symbols under discussion, being precoded,actually include both symbols s1 and s2.) Accordingly, no change inphase is performed on the pilot symbols inserted in z2′.

FIGS. 48A and 48B illustrate the frame configuration of modulatedsignals (precoded baseband signals) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 48A illustrates the frame configuration ofmodulated signal (precoded baseband signal) z1 or z1′ while FIG. 48Billustrates the frame configuration of modulated signal (precodedbaseband signal) z2′. In FIGS. 48A and 48B, 4701 marks pilot symbolswhile 4702 marks data symbols. The data symbols 4702 are symbols onwhich precoding or precoding and a change in phase have been performed.

FIGS. 48A and 48B, like FIG. 26, indicate the arrangement of symbolswhen a change of phase is applied to precoded baseband signal z1′ and toprecoded baseband signal z2′. (Although FIG. 26 illustrates a change inphase with respect to the time domain, switching time t with carrier fin FIG. 26 corresponds to a change in phase with respect to thefrequency domain. In other words, replacing (t) with (t, f) where t istime and f is frequency corresponds to performing a change of phase ontime-frequency blocks.) Accordingly, the numerical values indicated inFIGS. 48A and 48B for each of the symbols are the values of precodedbaseband signal z1′ and z2′ after a change of phase.

The key point of FIGS. 48A and 48B is that a change of phase isperformed on the data symbols of precoded baseband signal z1′, that is,on the precoded symbols thereof, and on the data symbols of precodedbaseband signal z2′, that is, on the precoded symbols thereof. (Thesymbols under discussion, being precoded, actually include both symbolss1 and s2.) Accordingly, no change in phase is performed on the pilotsymbols inserted in z1′, nor on the pilot symbols inserted in z2′.

FIGS. 49A and 49B illustrate the frame configuration of modulatedsignals (precoded baseband signals) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 49A illustrates the frame configuration ofmodulated signal (precoded baseband signal) z1 or z1′ while FIG. 49Billustrates the frame configuration of modulated signal (precodedbaseband signal) z2′. In FIGS. 49A and 49B, 4701 marks pilot symbols,4702 marks data symbols, and 4901 marks null symbols for which thein-phase component of the baseband signal I=0 and the quadraturecomponent Q=0. As such, data symbols 4702 are symbols on which precodingor precoding and a change in phase have been performed. FIGS. 49A and49B differ from FIGS. 47A and 47B in the configuration method forsymbols other than data symbols. The times and carriers at which pilotsymbols are inserted into modulated signal z1′ are null symbols inmodulated signal z2′. Conversely, the times and carriers at which pilotsymbols are inserted into modulated signal z2′ are null symbols inmodulated signal z1′.

FIGS. 49A and 49B, like FIG. 6, indicate the arrangement of symbols whena change in phase is applied to precoded baseband signal z2′ (while nochange of phase is performed on precoded baseband signal z1). (AlthoughFIG. 6 illustrates a change in phase with respect to the time domain,switching time t with carrier f in FIG. 6 corresponds to a change inphase with respect to the frequency domain. In other words, replacing(t) with (t, f) where t is time and f is frequency corresponds toperforming a change of phase on time-frequency blocks.) Accordingly, thenumerical values indicated in FIGS. 49A and 49B for each of the symbolsare the values of precoded baseband signal z2′ after a change of phaseis performed. No values are given for the symbols of precoded basebandsignal z1′ (z1) as no change of phase is performed thereon.

The key point of FIGS. 49A and 49B is that a change of phase isperformed on the data symbols of precoded baseband signal z2′, i.e., onprecoded symbols. (The symbols under discussion, being precoded,actually include both symbols s1 and s2.) Accordingly, no change inphase is performed on the pilot symbols inserted in z2′.

FIGS. 50A and 50B illustrate the frame configuration of modulatedsignals (precoded baseband signals) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 50A illustrates the frame configuration ofmodulated signal (precoded baseband signal) z1 or z1′ while FIG. 50Billustrates the frame configuration of modulated signal (precodedbaseband signal) z2′. In FIGS. 50A and 50B, 4701 marks pilot symbols,4702 marks data symbols, and 4901 marks null symbols for which thein-phase component of the baseband signal I=0 and the quadraturecomponent Q=0. As such, data symbols 4702 are symbols on which precodingor precoding and a change in phase have been performed. FIGS. 50A and50B differ from FIGS. 48A and 48B in the configuration method forsymbols other than data symbols. The times and carriers at which pilotsymbols are inserted into modulated signal z1′ are null symbols inmodulated signal z2′. Conversely, the times and carriers at which pilotsymbols are inserted into modulated signal z2′ are null symbols inmodulated signal z1′.

FIGS. 50A and 50B, like FIG. 26, indicate the arrangement of symbolswhen a change of phase is applied to precoded baseband signal z1′ and toprecoded baseband signal z2′. (Although FIG. 26 illustrates a change inphase with respect to the time domain, switching time t with carrier fin FIG. 26 corresponds to a change in phase with respect to thefrequency domain. In other words, replacing (t) with (t, f) where t istime and f is frequency corresponds to performing a change of phase ontime-frequency blocks.) Accordingly, the numerical values indicated inFIGS. 50A and 50B for each of the symbols are the values of precodedbaseband signal z1′ and z2′ after the change in phase.

The key point of FIGS. 50A and 50B is that a change of phase isperformed on the data symbols of precoded baseband signal z1′, that is,on the precoded symbols thereof, and on the data symbols of precodedbaseband signal z2′, that is, on the precoded symbols thereof. (Thesymbols under discussion, being precoded, actually include both symbolss1 and s2.) Accordingly, no change in phase is performed on the pilotsymbols inserted in z1′, nor on the pilot symbols inserted in z2′.

FIG. 51 illustrates a sample configuration of a transmission devicegenerating and transmitting modulated signal having the frameconfiguration of FIGS. 47A, 47B, 49A, and 49B. Components thereofperforming the same operations as those of FIG. 4 use the same referencesymbols thereas.

In FIG. 51, the weighting units 308A and 308B and phase changer 317Bonly operate at times indicated by the frame configuration signal 313 ascorresponding to data symbols.

In FIG. 51, a pilot symbol generator 5101 (that also generates nullsymbols) outputs baseband signals 5102A and 5102B for a pilot symbolwhenever the frame configuration signal 313 indicates a pilot symbol(and a null symbol).

Although not indicated in the frame configurations from FIGS. 47Athrough 50B, when precoding (or phase rotation) is not performed, suchas when transmitting a modulated signal using only one antenna (suchthat the other antenna transmits no signal) or when using a space-timecoding transmission method (particularly, space-time block coding) totransmit control information symbols, then the frame configurationsignal 313 takes control information symbols 5104 and controlinformation 5103 as input. When the frame configuration signal 313indicates a control information symbol, baseband signals 5102A and 5102Bthereof are output.

Wireless units 310A and 310B of FIG. 51 take a plurality of basebandsignals as input and select a desired baseband signal according to theframe configuration signal 313. The wireless units 310A and 310B thenapply OFDM signal processing and output modulated signals 311A and 311Bconforming to the frame configuration.

FIG. 52 illustrates a sample configuration of a transmission devicegenerating and transmitting modulated signal having the frameconfiguration of FIGS. 48A, 48B, 50A, and 50B. Components thereofperforming the same operations as those of FIGS. 4 and 51 use the samereference symbols thereas. FIG. 51 features an additional phase changer317A that only operates when the frame configuration signal 313indicates a data symbol. At all other times, the operations areidentical to those explained for FIG. 51.

FIG. 53 illustrates a sample configuration of a transmission device thatdiffers from that of FIG. 51. The following describes the points ofdifference. As shown in FIG. 53, phase changer 317B takes a plurality ofbaseband signals as input. Then, when the frame configuration signal 313indicates a data symbol, phase changer 317B performs the change in phaseon precoded baseband signal 316B. When frame configuration signal 313indicates a pilot symbol (or null symbol) or a control informationsymbol, phase changer 317B pauses phase changing operations such thatthe symbols of the baseband signal are output as-is. (This may beinterpreted as performing forced rotation corresponding to e^(j0).)

A selector 5301 takes the plurality of baseband signals as input andselects a baseband signal having a symbol indicated by the frameconfiguration signal 313 for output.

FIG. 54 illustrates a sample configuration of a transmission device thatdiffers from that of FIG. 52. The following describes the points ofdifference. As shown in FIG. 54, phase changer 317B takes a plurality ofbaseband signals as input. Then, when the frame configuration signal 313indicates a data symbol, phase changer 317B performs the change in phaseon precoded baseband signal 316B. When frame configuration signal 313indicates a pilot symbol (or null symbol) or a control informationsymbol, phase changer 317B pauses phase changing operations such thatthe symbols of the baseband signal are output as-is. (This may beinterpreted as performing forced rotation corresponding to e^(j0).)

Similarly, as shown in FIG. 54, phase changer 5201 takes a plurality ofbaseband signals as input. Then, when the frame configuration signal 313indicates a data symbol, phase changer 5201 performs the change in phaseon precoded baseband signal 309A. When frame configuration signal 313indicates a pilot symbol (or null symbol) or a control informationsymbol, phase changer 5201 pauses phase changing operations such thatthe symbols of the baseband signal are output as-is. (This may beinterpreted as performing forced rotation corresponding to e^(j0)).

The above explanations are given using pilot symbols, control symbols,and data symbols as examples. However, the present invention is notlimited in this manner. When symbols are transmitted using methods otherthan precoding, such as single-antenna transmission or transmissionusing space-time block coding, not performing a change of phase isimportant. Conversely, performing a change of phase on symbols that havebeen precoded is the key point of the present invention.

Accordingly, a characteristic feature of the present invention is thatthe change of phase is not performed on all symbols within the frameconfiguration in the time-frequency domain, but only performed onsignals that have been precoded.

Embodiment 4

Embodiments 1 and 2, described above, discuss a regular change of phase.Embodiment 3, however, discloses performing a different change of phaseon neighbouring symbols.

The present Embodiment describes a phase changing method that variesaccording to the modulation scheme and the coding rate of theerror-correcting codes used by the transmission device.

Table 1, below, is a list of phase changing method settingscorresponding to the settings and parameters of the transmission device.

TABLE 1 No. of Modulated Phase Transmission Modulation Changing SignalsScheme Coding Rate Pattern 2 #1: QPSK, #1: 1/2, #1: —, #2: QPSK #2 2/3#2: A 2 #1: QPSK, #1: 1/2, #1: A, #2: QPSK #2: 3/4 #2: B 2 #1: QPSK, #1:2/3, #1: A, #2: QPSK #2: 3/5 #2: C 2 #1: QPSK, #1: 2/3, #1: C, #2: QPSK#2: 2/3 #2: — 2 #1: QPSK, #1: 3/3, #1: D, #2: QPSK #2: 5/6 #2: E 2 #1:QPSK, #1: 1/2, #1: B, #2: 16-QAM #2: 2/3 #2: A 2 #1: QPSK, #1: 1/2, #1:A, #2: 16-QAM #2: 3/4 #2: C 2 #1: QPSK, #1: 1/2, #1: —, #2: 16-QAM #2:3/5 #2: E 2 #1: QPSK, #1: 2/3, #1: D, #2: 16-QAM #2: 3/4 #2: — 2 #1:QPSK, #1: 2/3, #1: D, #2: 16-QAM #2: 5/6 #2: B 2 #1: 16-QAM, #1: 1/2,#1: —, #2: 16-QAM #2: 2/3 #2: E . . . . . . . . . . . .

In Table 1, #1 denotes modulated signal s1 from Embodiment 1 describedabove (baseband signal s1 modulated with the modulation scheme set bythe transmission device) and #2 denotes modulated signal s2 (basebandsignal s2 modulated with the modulation scheme set by the transmissiondevice). The coding rate column of Table 1 indicates the coding rate ofthe error-correcting codes for modulation schemes #1 and #2. The phasechanging pattern column of Table 1 indicates the phase changing methodapplied to precoded baseband signals z1 (z1′) and z2 (z2′), as explainedin Embodiments 1 through 3. Although the phase changing patterns arelabelled A, B, C, D, E, and so on, this refers to the phase changedegree applied, for example, in a phase changing pattern given by Math.46 (formula 46) and Math. 47 (formula 47), above. In the phase changingpattern column of Table 1, the dash signifies that no change of phase isapplied.

The combinations of modulation scheme and coding rate listed in Table 1are examples. Other modulation schemes (such as 128-QAM and 256-QAM) andcoding rates (such as ⅞) not listed in Table 1 may also be included.Also, as described in Embodiment 1, the error-correcting codes used fors1 and s2 may differ (Table 1 is given for cases where a single type oferror-correcting codes is used, as in FIG. 4). Furthermore, the samemodulation scheme and coding rate may be used with different phasechanging patterns. The transmission device transmits informationindicating the phase changing patterns to the reception device. Thereception device specifies the phase changing pattern bycross-referencing the information and Table 1, then performsdemodulation and decoding. When the modulation scheme anderror-correction method determine a unique phase changing pattern, thenas long as the transmission device transmits the modulation scheme andinformation regarding the error-correction method, the reception deviceknows the phase changing pattern by obtaining that information. As such,information pertaining to the phase changing pattern is not strictlynecessary.

In Embodiments 1 through 3, the change of phase is applied to precodedbaseband signals. However, the amplitude may also be modified along withthe phase in order to apply periodical, regular changes. Accordingly, anamplification modification pattern regularly modifying the amplitude ofthe modulated signals may also be made to conform to Table 1. In suchcircumstances, the transmission device should include an amplificationmodifier that modifies the amplification after weighting unit 308A orweighting unit 308B from FIG. 3 or 4. In addition, amplificationmodification may be performed on only one of or on both of the precodedbaseband signals z1(t) and z2(t) (in the former case, the amplificationmodifier is only needed after one of weighting unit 308A and 308B).

Furthermore, although not indicated in Table 1 above, the mapping schememay also be regularly modified by the mapper, without a regular changeof phase.

That is, when the mapping method for modulated signal s1(t) is 16-QAMand the mapping method for modulated signal s2(t) is also 16-QAM, themapping method applied to modulated signal s2(t) may be regularlychanged as follows: from 16-QAM to 16-APSK, to 16-QAM in the I-Q plane,to a first mapping method producing signal point distribution unlike16-APSK, to 16-QAM in the I-Q plane, to a second mapping methodproducing signal point distribution unlike 16-APSK, and so on. As such,the data reception quality can be improved for the reception device,much like the results obtained by a regular change of phase describedabove.

In addition, the present invention may use any combination of methodsfor a regular change of phase, mapping method, and amplitude, and thetransmit signal may transmit with all of these taken into consideration.

The present Embodiment may be realized using single-carrier methods aswell as multi-carrier methods. Accordingly, the present Embodiment mayalso be realized using, for example, spread-spectrum communications,OFDM, SC-FDM, SC-OFDM, wavelet OFDM as described in Non-PatentLiterature 7, and so on. As described above, the present Embodimentdescribes changing the phase, amplitude, and mapping methods byperforming phase, amplitude, and mapping method modifications withrespect to the time domain t. However, much like Embodiment 1, the samechanges may be carried out with respect to the frequency domain. Thatis, considering the phase, amplitude, and mapping method modification inthe time domain t described in the present Embodiment and replacing twith f (f being the ((sub-) carrier) frequency) leads to phase,amplitude, and mapping method modification applicable to the frequencydomain. Also, the phase, amplitude, and mapping method modification ofthe present Embodiment is also applicable to phase, amplitude, andmapping method modification in both the time domain and the frequencydomain.

Furthermore, in the present Embodiment, symbols other than data symbols,such as pilot symbols (preamble, unique word, etc) or symbolstransmitting control information, may be arranged within the frame inany manner.

Embodiment A1

The present Embodiment describes a method of regularly changing thephase when encoding is performed using block codes as described inNon-Patent Literature 12 through 15, such as QC (Quasi-Cyclic) LDPCCodes (not only QC-LDPC but also LDPC codes may be used), concatenatedLDPC and BCH (Bose-Chaudhuri-Hocquenghem) codes, Turbo codes orDuo-Binary Turbo codes using tail-biting, and so on. The followingexample considers a case where two streams s1 and s2 are transmitted.When encoding has been performed using block codes and controlinformation and the like is not necessary, the number of bits making upeach coded block matches the number of bits making up each block code(control information and so on described below may yet be included).When encoding has been performed using block codes or the like andcontrol information or the like (e.g., CRC transmission parameters) isrequired, then the number of bits making up each coded block is the sumof the number of bits making up the block codes and the number of bitsmaking up the information.

FIG. 34 illustrates the varying numbers of symbols and slots needed ineach coded block when block codes are used. FIG. 34 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 4, and thetransmission device has only one encoder. (Here, the transmission methodmay be any single-carrier method or multi-carrier method such as OFDM.)

As shown in FIG. 34, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

Then, given that the transmission device from FIG. 4 transmits twostreams simultaneously, 1500 of the aforementioned 3000 symbols neededwhen the modulation scheme is QPSK are assigned to s1 and the other 1500symbols are assigned to s2. As such, 1500 slots for transmitting the1500 symbols (hereinafter, slots) are required for each of s1 and s2.

By the same reasoning, when the modulation scheme is 16-QAM, 750 slotsare needed to transmit all of the bits making up each coded block, andwhen the modulation scheme is 64-QAM, 500 slots are needed to transmitall of the bits making up each coded block.

The following describes the relationship between the above-defined slotsand the phase of multiplication, as pertains to methods for a regularchange of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase. That is, five different phase changing values (or phasechanging sets) have been prepared for the phase changer of thetransmission device from FIG. 4 (equivalent to the period (cycle) fromEmbodiments 1 through 4) (As in FIG. 6, five phase changing values areneeded in order to perform a change of phase with a period (cycle) offive on precoded baseband signal z2′ only. Also, as in FIG. 26, twophase changing values are needed for each slot in order to perform thechange of phase on both precoded baseband signals z1′ and z2′. These twophase changing values are termed a phase changing set. Accordingly, fivephase changing sets should ideally be prepared in order to perform achange of phase having a period (cycle) of five in such circumstances).These five phase changing values (or phase changing sets) are expressedas PHASE[0], PHASE[1], PHASE[2], PHASE[3], and PHASE[4].

For the above-described 1500 slots needed to transmit the 6000 bitsmaking up a single coded block when the modulation scheme is QPSK,PHASE[0] is used on 300 slots, PHASE[1] is used on 300 slots, PHASE[2]is used on 300 slots, PHASE[3] is used on 300 slots, and PHASE[4] isused on 300 slots. This is due to the fact that any bias in phase usagecauses great influence to be exerted by the more frequently used phase,and that the reception device is dependent on such influence for datareception quality.

Further still, for the above-described 500 slots needed to transmit the6000 bits making up a single coded block when the modulation scheme is64-QAM, PHASE[0] is used on 150 slots, PHASE[1] is used on 150 slots,PHASE[2] is used on 150 slots, PHASE[3] is used on 150 slots, andPHASE[4] is used on 150 slots.

Further still, for the above-described 500 slots needed to transmit the6000 bits making up a single coded block when the modulation scheme is64-QAM, PHASE[0] is used on 100 slots, PHASE[1] is used on 100 slots,PHASE[2] is used on 100 slots, PHASE[3] is used on 100 slots, andPHASE[4] is used on 100 slots.

As described above, a method for a regular change of phase requires thepreparation of N phase changing values (or phase changing sets) (wherethe N different phases are expressed as PHASE[0], PHASE[1], PHASE[2] . .. PHASE[N−2], PHASE[N−1]). As such, in order to transmit all of the bitsmaking up a single coded block, PHASE[0] is used on K₀ slots, PHASE[1]is used on K₁ slots, PHASE[i] is used on K_(i) slots (where i=0, 1, 2 .. . N−1), and PHASE[N−1] is used on K_(N−1) slots, such that Condition#A01 is met.

(Condition #A01)

K₀=K₁ . . . =K_(i)= . . . K_(N−1). That is, K_(a)=K_(b) (∀a and ∀b wherea, b,=0, 1, 2 . . . N−1; (a and b being integers between 0 and N−1),a≠b).

Then, when a communication system that supports multiple modulationschemes selects one such supported modulation scheme for use, Condition#A01 is met for the supported modulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #A01 may not be satisfied for some modulation schemes. In sucha case, the following condition applies instead of Condition #A01.

(Condition #A02)

The difference between K_(a) and K_(b) is 0 or 1. That is, |K_(a)−K_(b)|is 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (a and b being integersbetween 0 and N−1), a≠b)

FIG. 35 illustrates the varying numbers of symbols and slots needed ineach coded block when block codes are used. FIG. 35 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 3 and FIG.12, and the transmission device has two encoders. (Here, thetransmission method may be any single-carrier method or multi-carriermethod such as OFDM.)

As shown in FIG. 35, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

The transmission device from FIG. 3 and the transmission device fromFIG. 12 each transmit two streams at once, and have two encoders. Assuch, the two streams each transmit different code blocks. Accordingly,when the modulation scheme is QPSK, two coded blocks drawn from s1 ands2 are transmitted within the same interval, e.g., a first coded blockdrawn from s1 is transmitted, then a second coded block drawn from s2 istransmitted. As such, 3000 slots are needed in order to transmit thefirst and second coded blocks.

By the same reasoning, when the modulation scheme is 16-QAM, 1500 slotsare needed to transmit all of the bits making up the two coded blocks,and when the modulation scheme is 64-QAM, 1000 slots are needed totransmit all of the bits making up the two coded blocks

The following describes the relationship between the above-defined slotsand the phase of multiplication, as pertains to methods for a regularchange of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase. That is, five different phase changing values (or phasechanging sets) have been prepared for the phase changer of thetransmission device from FIGS. 3 and 12 (equivalent to the period(cycle) from Embodiments 1 through 4) (As in FIG. 6, five phase changingvalues are needed in order to perform a change of phase with a period(cycle) of five on precoded baseband signal z2′ only. Also, as in FIG.26, two phase changing values are needed for each slot in order toperform the change of phase on both precoded baseband signals z1′ andz2′. These two phase changing values are termed a phase changing set.Accordingly, five phase changing sets should ideally be prepared inorder to perform a change of phase having a period (cycle) of five insuch circumstances). These five phase changing values (or phase changingsets) are expressed as PHASE[0], PHASE[1], PHASE[2], PHASE[3], and PHASE[4].

For the above-described 3000 slots needed to transmit the 6000×2 bitsmaking up the two coded blocks when the modulation scheme is QPSK,PHASE[0] is used on 600 slots, PHASE[1] is used on 600 slots, PHASE[2]is used on 600 slots, PHASE[3] is used on 600 slots, and PHASE[4] isused on 600 slots. This is due to the fact that any bias in phase usagecauses great influence to be exerted by the more frequently used phase,and that the reception device is dependent on such influence for datareception quality.

Furthermore, in order to transmit the first coded block, PHASE[0] isused on slots 600 times, PHASE[1] is used on slots 600 times, PHASE[2]is used on slots 600 times, PHASE[3] is used on slots 600 times, andPHASE[4] is used on slots 600 times. Furthermore, in order to transmitthe second coded block, PHASE[0] is used on slots 600 times, PHASE[1] isused on slots 600 times, PHASE[2] is used on slots 600 times, PHASE[3]is used on slots 600 times, and PHASE[4] is used on slots 600 times.

Similarly, for the above-described 1500 slots needed to transmit the6000×2 bits making up the two coded blocks when the modulation scheme is16-QAM, PHASE[0] is used on 300 slots, PHASE[1] is used on 300 slots,PHASE[2] is used on 300 slots, PHASE[3] is used on 300 slots, andPHASE[4] is used on 300 slots.

Furthermore, in order to transmit the first coded block, PHASE[0] isused on slots 300 times, PHASE[1] is used on slots 300 times, PHASE[2]is used on slots 300 times, PHASE[3] is used on slots 300 times, andPHASE[4] is used on slots 300 times. Furthermore, in order to transmitthe second coded block, PHASE[0] is used on slots 300 times, PHASE[1] isused on slots 300 times, PHASE[2] is used on slots 300 times, PHASE[3]is used on slots 300 times, and PHASE[4] is used on slots 300 times.

Similarly, for the above-described 1000 slots needed to transmit the6000×2 bits making up the two coded blocks when the modulation scheme is64-QAM, PHASE[0] is used on 200 slots, PHASE[1] is used on 200 slots,PHASE[2] is used on 200 slots, PHASE[3] is used on 200 slots, andPHASE[4] is used on 200 slots.

Furthermore, in order to transmit the first coded block, PHASE[0] isused on slots 200 times, PHASE[1] is used on slots 200 times, PHASE[2]is used on slots 200 times, PHASE[3] is used on slots 200 times, andPHASE[4] is used on slots 200 times. Furthermore, in order to transmitthe second coded block, PHASE[0] is used on slots 200 times, PHASE[1] isused on slots 200 times, PHASE[2] is used on slots 200 times, PHASE[3]is used on slots 200 times, and PHASE[4] is used on slots 200 times.

As described above, a method for regularly changing the phase requiresthe preparation of phase changing values (or phase changing sets)expressed as PHASE[0], PHASE[1], PHASE[2] . . . PHASE[N−2], PHASE[N−1].As such, in order to transmit all of the bits making up two codedblocks, PHASE[0] is used on K₀ slots, PHASE[1] is used on K₁ slots,PHASE[i] is used on K_(i) slots (where i=0, 1, 2 . . . N−1), andPHASE[N−1] is used on K_(N−1) slots, such that Condition #A03 is met.

(Condition #A03)

K₀=K₁ . . . =K_(i)= . . . K_(N−1). That is, K_(a)=K_(b) (∀a and ∀b wherea, b,=0, 1, 2 . . . N−1 (a and b being integers between 0 and N−1),a≠b).Further, in order to transmit all of the bits making up the first codedblock, PHASE[0] is used K_(0,1) times, PHASE[1] is used K₁₁ times,PHASE[i] is used K_(i,1) times (where i=0, 1, 2 . . . N−1), andPHASE[N−1] is used K_(N−1,1) times, such that Condition #A04 is met.

(Condition #A04)

K_(0,1)=K_(1,1)= . . . K_(i,1)= . . . K_(N−1,1). That is,K_(a,1)=K_(b,1) (∀a and ∀b where a, b,=0, 1, 2 . . . N−1 (a and b beingintegers between 0 and N−1), a≠b).Furthermore, in order to transmit all of the bits making up the secondcoded block, PHASE[0] is used K_(0,2) times, PHASE[1] is used K_(1,2)times, PHASE[i] is used K_(i,2) times (where i=0, 1, 2 . . . N−1), andPHASE[N−1] is used K_(N−1,2) times, such that Condition #A05 is met.

(Condition #A05)

K_(0,2)=K_(1,2)= . . . K_(i,2)= . . . K_(N−1,2). That is,K_(a,2)=K_(b,2) (∀a and ∀b where a, b,=0, 1, 2 . . . N−1 (a and b beingintegers between 0 and N−1), a≠b).

Then, when a communication system that supports multiple modulationschemes selects one such supported modulation scheme for use, Condition#A03, #A04, and #A05 is met for the supported modulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbol (though some may happen to use the same number),Conditions #A03, #A04, and #A05 may not be satisfied for some modulationschemes. In such a case, the following conditions apply instead ofCondition #A03, #A04, and #A05.

(Condition #A06)

The difference between K_(a) and K_(b) satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (aand b being integers between 0 and N−1), a≠b)

(Condition #A07)

The difference between K_(a,1) and K_(b,1) satisfies 0 or 1. That is,|K_(a,1)−K_(b,1)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1(a and b being integers between 0 and N−1), a≠b)

(Condition #A08)

The difference between K_(a,2) and K_(b,2) satisfies 0 or 1. That is,|K_(a2)−Kb,2| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (aand b being integers between 0 and N−1), a≠b)

As described above, bias among the phases being used to transmit thecoded blocks is removed by creating a relationship between the codedblock and the phase of multiplication. As such, data reception qualitymay be improved for the reception device.

In the present Embodiment, N phase changing values (or phase changingsets) are needed in order to perform a change of phase having a period(cycle) of N with the method for a regular change of phase. As such, Nphase changing values (or phase changing sets) PHASE[0], PHASE[1],PHASE[2] . . . PHASE[N−2], and PHASE[N−1] are prepared. However, schemesexist for reordering the phases in the stated order with respect to thefrequency domain. No limitation is intended in this regard. The N phasechanging values (or phase changing sets) may also change the phases ofblocks in the time domain or in the time-frequency domain to obtain asymbol arrangement as described in Embodiment 1. Although the aboveexamples discuss a phase changing method with a period (cycle) of N, thesame effects are obtainable using N phase changing values (or phasechanging sets) at random. That is, the N phase changing values (or phasechanging sets) need not always have regular periodicity. As long as theabove-described conditions are satisfied, great quality data receptionimprovements are realizable for the reception device.

Furthermore, given the existence of modes for spatial multiplexing MIMOschemes, MIMO schemes using a fixed precoding matrix, space-time blockcoding schemes, single-stream transmission, and schemes using a regularchange of phase (the transmission schemes described in Embodiments 1through 4), the transmission device (broadcaster, base station) mayselect any one of these transmission schemes.

As described in Non-Patent Literature 3, spatial multiplexing MIMOmethods involve transmitting signals s1 and s2, which are mapped using aselected modulation scheme, on each of two different antennas. Asdescribed in Embodiments 1 through 4, MIMO methods using a fixedprecoding matrix involve performing precoding only (with no change ofphase). Further, space-time block coding methods are described inNon-Patent Literature 9, 16, and 17. Single-stream transmission methodsinvolve transmitting signal s1, mapped with a selected modulationscheme, from an antenna after performing predetermined processing.

Schemes using multi-carrier transmission such as OFDM involve a firstcarrier group made up of a plurality of carriers and a second carriergroup made up of a plurality of carriers different from the firstcarrier group, and so on, such that multi-carrier transmission isrealized with a plurality of carrier groups. For each carrier group, anyof spatial multiplexing MIMO schemes, MIMO schemes using a fixedprecoding matrix, space-time block coding schemes, single-streamtransmission, and schemes using a regular change of phase may be used.In particular, schemes using a regular change of phase on a selected(sub-)carrier group are preferably used to realize the presentEmbodiment.

When a change of phase is performed, then for example, a phase changingvalue for PHASE[i] of X radians is performed on only one precodedbaseband signal, the phase changers of FIGS. 3, 4, 5, 12, 25, 29, 51,and 53 multiplies precoded baseband signal z2′ by e^(jX). Then, when achange of phase by, for example, a phase changing set for PHASE[i] of Xradians and Y radians is performed on both precoded baseband signals,the phase changers from FIGS. 26, 27, 28, 52, and 54 multiply precodedbaseband signal z2′ by e^(jX) and multiply precoded baseband signal z1′by e^(jY).

Embodiment B1

The following describes a sample configuration of an application of thetransmission methods and reception methods discussed in the aboveembodiments and a system using the application.

FIG. 36 illustrates the configuration of a system that includes devicesexecuting transmission methods and reception methods described in theabove Embodiments. As shown in FIG. 36, the devices executingtransmission methods and reception methods described in the aboveEmbodiments include various receivers such as a broadcaster, atelevision 3611, a DVD recorder 3612, a STB (set-top box) 3613, acomputer 3620, a vehicle-mounted television 3641, a mobile phone 3630and so on within a digital broadcasting system 3600. Specifically, thebroadcaster 3601 uses a transmission method discussed in theabove-described Embodiments to transmit multiplexed data, in whichvideo, audio, and other data are multiplexed, over a predeterminedtransmission band.

The signals transmitted by the broadcaster 3601 are received by anantenna (such as antenna 3660 or 3640) embedded within or externallyconnected to each of the receivers. Each receiver obtains themultiplexed data by using reception methods discussed in theabove-described Embodiments to demodulate the signals received by theantenna. Accordingly, the digital broadcasting system 3600 is able torealize the effects of the present invention, as discussed in theabove-described Embodiments.

The video data included in the multiplexed data are coded with a videocoding method compliant with a standard such as MPEG-2 (Moving PictureExperts Group), MPEG4-AVC (Advanced Video Coding), VC-1, or the like.The audio data included in the multiplexed data are encoded with anaudio coding method compliant with a standard such as Dolby AC-3 (AudioCoding), Dolby Digital Plus, MLP (Meridian Lossless Packing), DTS(Digital Theatre Systems), DTS-HD, Linear PCM (Pulse-Code Modulation),or the like.

FIG. 37 illustrates the configuration of a receiver 7900 that executes areception method described in the above-described Embodiments. Thereceiver 3700 corresponds to a receiver included in one of thetelevision 3611, the DVD recorder 3612, the STB 3613, the computer 3620,the vehicle-mounted television 3641, the mobile phone 3630 and so onfrom FIG. 36. The receiver 3700 includes a tuner 3701 converting ahigh-frequency signal received by an antenna 3760 into a basebandsignal, and a demodulator 3702 demodulating the baseband signal soconverted to obtain the multiplexed data. The demodulator 3702 executesa reception method discussed in the above-described Embodiments, andthus achieves the effects of the present invention as explained above.

The receiver 3700 further includes a stream interface 3720 thatdemultiplexes the audio and video data in the multiplexed data obtainedby the demodulator 3702, a signal processor 3704 that decodes the videodata obtained from the demultiplexed video data into a video signal byapplying a video decoding method corresponding thereto and decodes theaudio data obtained from the demultiplexed audio data into an audiosignal by applying an audio decoding method corresponding thereto, anaudio output unit 3706 that outputs the decoded audio signal through aspeaker or the like, and a video display unit 3707 that outputs thedecoded video signal on a display or the like.

When, for example, a user uses a remote control 3750, information for aselected channel (selected (television) program or audio broadcast) istransmitted to an operation input unit 3710. Then, the receiver 3700performs processing on the received signal received by the antenna 3760that includes demodulating the signal corresponding to the selectedchannel, performing error-correcting decoding, and so on, in order toobtain the received data. At this point, the receiver 3700 obtainscontrol symbol information that includes information on the transmissionmethod (the transmission method, modulation scheme, error-correctionmethod, and so on from the above-described Embodiments) (as describedusing FIGS. 5 and 41) from control symbols included the signalcorresponding to the selected channel. As such, the receiver 3700 isable to correctly set the reception operations, demodulation scheme,error-correction method and so on, thus enabling the data included inthe data symbols transmitted by the broadcaster (base station) to beobtained. Although the above description is given for an example of theuser using the remote control 3750, the same operations apply when theuser presses a selection key embedded in the receiver 3700 to select achannel.

According to this configuration, the user is able to view programsreceived by the receiver 3700.

The receiver 3700 pertaining to the present Embodiment further includesa drive 3708 that may be a magnetic disk, an optical disc, anon-volatile semiconductor memory, or a similar recording medium. Thereceiver 3700 stores data included in the demultiplexed data obtainedthrough demodulation by the demodulator 3702 and error-correctingdecoding (in some circumstances, the data obtained through demodulationby the demodulator 3702 may not be subject to error correction. Also,the receiver 3700 may perform further processing after error correction.The same hereinafter applies to similar statements concerning othercomponents), data corresponding to such data (e.g., data obtainedthrough compression of such data), data obtained through audio and videoprocessing, and so on, on the drive 3708. Here, an optical disc is arecording medium, such as DVD (Digital Versatile Disc) or BD (Blu-rayDisc), that is readable and writable with the use of a laser beam. Amagnetic disk is a floppy disk, a hard disk, or similar recording mediumon which information is storable through the use of magnetic flux tomagnetize a magnetic body. A non-volatile semiconductor memory is arecording medium, such as flash memory or ferroelectric random accessmemory, composed of semiconductor element(s). Specific examples ofnon-volatile semiconductor memory include an SD card using flash memoryand a Flash SSD (Solid State Drive). Naturally, the specific types ofrecording media mentioned herein are merely examples. Other types ofrecording mediums may also be used.

According to this structure, the user is able to record and storeprograms received by the receiver 3700, and is thereby able to viewprograms at any given time after broadcasting by reading out therecorded data thereof.

Although the above explanations describe the receiver 3700 storingmultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding on the drive 3708, a portion of the dataincluded in the multiplexed data may instead be extracted and recorded.For example, when data broadcasting services or similar content isincluded along with the audio and video data in the multiplexed dataobtained through demodulation by the demodulator 3702 anderror-correcting decoding, the audio and video data may be extractedfrom the multiplexed data demodulated by the demodulator 3702 and storedas new multiplexed data. Furthermore, the drive 3708 may store eitherthe audio data or the video data included in the multiplexed dataobtained through demodulation by the demodulator 3702 anderror-correcting decoding as new multiplexed data. The aforementioneddata broadcasting service content included in the multiplexed data mayalso be stored on the drive 3708.

Furthermore, when a television, recording device (e.g., a DVD recorder,BD recorder HDD recorder, SD card, or similar), or mobile phoneincorporating the receiver 3700 of the present invention receivesmultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding that includes data for correcting bugs insoftware used to operate the television or recording device, forcorrecting bugs in software for preventing personal information andrecorded data from being leaked, and so on, such software bugs may becorrected by installing the data on the television or recording device.As such, bugs in the receiver 3700 are corrected through the inclusionof data for correcting bugs in the software of the receiver 3700.Accordingly, the television, recording device, or mobile phoneincorporating the receiver 3700 may be made to operate more reliably.

Here, the process of extracting a portion of the data included in themultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding is performed by, for example, the streaminterface 3703. Specifically, the stream interface 3703, demultiplexesthe various data included in the multiplexed data demodulated by thedemodulator 3702, such as audio data, video data, data broadcastingservice content, and so on, as instructed by a non-diagrammed controllersuch as a CPU. The stream interface 3703 then extracts and multiplexesonly the indicated demultiplexed data, thus generating new multiplexeddata. The data to be extracted from the demultiplexed data may bedetermined by the user or may be determined in advance according to thetype of recording medium.

According to such a structure, the receiver 3700 is able to extract andrecord only the data needed in order to view the recorded program. Assuch, the amount of data to be recorded can be reduced.

Although the above explanation describes the drive 3708 as storingmultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding, the video data included in themultiplexed data so obtained may be converted by using a different videocoding method than the original video coding method applied thereto, soas to reduce the amount of data or the bit rate thereof. The drive 3708may then store the converted video data as new multiplexed data. Here,the video coding method used to generate the new video data may conformto a different standard than that used to generate the original videodata. Alternatively, the same video coding method may be used withdifferent parameters. Similarly, the audio data included in themultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding may be converted by using a differentaudio coding method than the original audio coding method appliedthereto, so as to reduce the amount of data or the bit rate thereof. Thedrive 3708 may then store the converted audio data as new multiplexeddata.

Here, the process by which the audio or video data included in themultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding is converted so as to reduce the amount ofdata or the bit rate thereof is performed by, for example, the streaminterface 3703 or the signal processor 3704. Specifically, the streaminterface 3703 demultiplexes the various data included in themultiplexed data demodulated by the demodulator 3702, such as audiodata, video data, data broadcasting service content, and so on, asinstructed by an undiagrammed controller such as a CPU. The signalprocessor 3704 then performs processing to convert the video data sodemultiplexed by using a different video coding method than the originalvideo coding method applied thereto, and performs processing to convertthe audio data so demultiplexed by using a different video coding methodthan the original audio coding method applied thereto. As instructed bythe controller, the stream interface 3703 then multiplexes the convertedaudio and video data, thus generating new multiplexed data. The signalprocessor 3704 may, in accordance with instructions from the controller,performing conversion processing on either the video data or the audiodata, alone, or may perform conversion processing on both types of data.In addition, the amounts of video data and audio data or the bit ratethereof to be obtained by conversion may be specified by the user ordetermined in advance according to the type of recording medium.

According to such a structure, the receiver 3700 is able to modify theamount of data or the bitrate of the audio and video data for storageaccording to the data storage capacity of the recording medium, oraccording to the data reading or writing speed of the drive 3708.Therefore, programs can be stored on the drive despite the storagecapacity of the recording medium being less than the amount ofmultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding, or the data reading or writing speed ofthe drive being lower than the bit rate of the demultiplexed dataobtained through demodulation by the demodulator 3702. As such, the useris able to view programs at any given time after broadcasting by readingout the recorded data.

The receiver 3700 further includes a stream output interface 3709 thattransmits the multiplexed data demultiplexed by the demodulator 3702 toexternal devices through a communications medium 3730. The stream outputinterface 3709 may be, for example, a wireless communication devicetransmitting modulated multiplexed data to an external device using awireless transmission method conforming to a wireless communicationstandard such as Wi-Fi™ (IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE802.11n, and so on), WiGiG, WirelessHD, Bluetooth™, ZigBee™, and so onthrough a wireless medium (corresponding to the communications medium3730). The stream output interface 3709 may also be a wiredcommunication device transmitting modulated multiplexed data to anexternal device using a communication method conforming to a wiredcommunication standard such as Ethernet™, USB (Universal Serial Bus),PLC (Power Line Communication), HDMI (High-Definition MultimediaInterface) and so on through a wired transmission path (corresponding tothe communications medium 3730) connected to the stream output interface3709.

According to this configuration, the user is able to use an externaldevice with the multiplexed data received by the receiver 3700 using thereception method described in the above-described Embodiments. The usageof multiplexed data by the user here includes use of the multiplexeddata for real-time viewing on an external device, recording of themultiplexed data by a recording unit included in an external device, andtransmission of the multiplexed data from an external device to a yetanother external device.

Although the above explanations describe the receiver 3700 outputtingmultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding through the stream output interface 3709,a portion of the data included in the multiplexed data may instead beextracted and output. For example, when data broadcasting services orsimilar content is included along with the audio and video data in themultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding, the audio and video data may be extractedfrom the multiplexed data obtained through demodulation by thedemodulator 3702 and error-correcting decoding, multiplexed and outputby the stream output interface 3709 as new multiplexed data. Inaddition, the stream output interface 3709 may store either the audiodata or the video data included in the multiplexed data obtained throughdemodulation by the demodulator 3702 and error-correcting decoding asnew multiplexed data.

Here, the process of extracting a portion of the data included in themultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding is performed by, for example, the streaminterface 3703. Specifically, the stream interface 3703 demultiplexesthe various data included in the multiplexed data demodulated by thedemodulator 3702, such as audio data, video data, data broadcastingservice content, and so on, as instructed by an undiagrammed controllersuch as a CPU. The stream interface 3703 then extracts and multiplexesonly the indicated demultiplexed data, thus generating new multiplexeddata. The data to be extracted from the demultiplexed data may bedetermined by the user or may be determined in advance according to thetype of stream output interface 3709.

According to this structure, the receiver 3700 is able to extract andoutput only the required data to an external device. As such, fewermultiplexed data are output using less communication bandwidth.

Although the above explanation describes the stream output interface3709 as outputting multiplexed data obtained through demodulation by thedemodulator 3702 and error-correcting decoding, the video data includedin the multiplexed data so obtained may be converted by using adifferent video coding method than the original video coding methodapplied thereto, so as to reduce the amount of data or the bit ratethereof. The stream output interface 3709 may then output the convertedvideo data as new multiplexed data. Here, the video coding method usedto generate the new video data may conform to a different standard thanthat used to generate the original video data. Alternatively, the samevideo coding method may be used with different parameters. Similarly,the audio data included in the multiplexed data obtained throughdemodulation by the demodulator 3702 and error-correcting decoding maybe converted by using a different audio coding method than the originalaudio coding method applied thereto, so as to reduce the amount of dataor the bit rate thereof. The stream output interface 3709 may thenoutput the converted audio data as new multiplexed data.

Here, the process by which the audio or video data included in themultiplexed data obtained through demodulation by the demodulator 3702and error-correcting decoding is converted so as to reduce the amount ofdata or the bit rate thereof is performed by, for example, the streaminterface 3703 or the signal processor 3704. Specifically, the streaminterface 3703 demultiplexes the various data included in themultiplexed data demodulated by the demodulator 3702, such as audiodata, video data, data broadcasting service content, and so on, asinstructed by an undiagrammed controller. The signal processor 3704 thenperforms processing to convert the video data so demultiplexed by usinga different video coding method than the original video coding methodapplied thereto, and performs processing to convert the audio data sodemultiplexed by using a different video coding method than the originalaudio coding method applied thereto. As instructed by the controller,the stream interface 3703 then multiplexes the converted audio and videodata, thus generating new multiplexed data. The signal processor 3704may, in accordance with instructions from the controller, performingconversion processing on either the video data or the audio data, alone,or may perform conversion processing on both types of data. In addition,the amounts of video data and audio data or the bit rate thereof to beobtained by conversion may be specified by the user or determined inadvance according to the type of stream output interface 3709.

According to this structure, the receiver 3700 is able to modify the bitrate of the video and audio data for output according to the speed ofcommunication with the external device. Thus, despite the speed ofcommunication with an external device being slower than the bit rate ofthe multiplexed data obtained through demodulation by the demodulator3702 and error-correcting decoding, by outputting new multiplexed datafrom the stream output interface to the external device, the user isable to use the new multiplexed data with other communication devices.

The receiver 3700 further includes an audiovisual output interface 3711that outputs audio and video signals decoded by the signal processor3704 to the external device through an external communications medium.The audiovisual output interface 3711 may be, for example, a wirelesscommunication device transmitting modulated audiovisual data to anexternal device using a wireless transmission method conforming to awireless communication standard such as Wi-Fi™ (IEEE 802.11a, IEEE802.11b, IEEE 802.11g, IEEE 802.11n, and so on), WiGig, WirelessHD,Bluetooth™, ZigBee™, and so on through a wireless medium. The streamoutput interface 3709 may also be a wired communication devicetransmitting modulated audiovisual data to an external device using acommunication method conforming to a wired communication standard suchas Ethernet™, USB, PLC, HDMI, and so on through a wired transmissionpath connected to the stream output interface 3709. Furthermore, thestream output interface 3709 may be a terminal for connecting a cablethat outputs analogue audio signals and video signals as-is.

According to such a structure, the user is able to use the audio signalsand video signals decoded by the signal processor 3704 with an externaldevice.

Further, the receiver 3700 includes an operation input unit 3710 thatreceives user operations as input. The receiver 3700 behaves inaccordance with control signals input by the operation input unit 3710according to user operations, such as by switching the power supply ONor OFF, changing the channel being received, switching subtitle displayON or OFF, switching between languages, changing the volume output bythe audio output unit 3706, and various other operations, includingmodifying the settings for receivable channels and the like.

The receiver 3700 may further include functionality for displaying anantenna level representing the received signal quality while thereceiver 3700 is receiving a signal. The antenna level may be, forexample, a index displaying the received signal quality calculatedaccording to the RSSI (Received Signal Strength Indicator), the receivedsignal magnetic field strength, the C/N (carrier-to-noise) ratio, theBER, the packet error rate, the frame error rate, the channel stateinformation, and so on, received by the receiver 3700 and indicating thelevel and the quality of a received signal. In such circumstances, thedemodulator 3702 includes a signal quality calibrator that measures theRSSI, the received signal magnetic field strength, the C/N ratio, theBER, the packet error rate, the frame error rate, the channel stateinformation, and so on. In response to user operations, the receiver3700 displays the antenna level (signal level, signal quality) in auser-recognizable format on the video display unit 3707. The displayformat for the antenna level (signal level, signal quality) may be anumerical value displayed according to the RSSI, the received signalmagnetic field strength, the C/N ratio, the BER, the packet error rate,the frame error rate, the channel state information, and so on, or maybe an image display that varies according to the RSSI, the receivedsignal magnetic field strength, the C/N ratio, the BER, the packet errorrate, the frame error rate, the channel state information, and so on.The receiver 3700 may display multiple antenna level (signal level,signal quality) calculated for each stream s1, s2, and so ondemultiplexed using the reception method discussed in theabove-described Embodiments, or may display a single antenna level(signal level, signal quality) calculated for all such streams. When thevideo data and audio data composing a program are transmittedhierarchically, the signal level (signal quality) may also be displayedfor each hierarchical level.

According to the above structure, the user is given an understanding ofthe antenna level (signal level, signal quality) numerically or visuallyduring reception using the reception methods discussed in theabove-described Embodiments.

Although the above example describes the receiver 3700 as including theaudio output unit 3706, the video display unit 3707, the drive 3708, thestream output interface 3709, and the audiovisual output interface 3711,all of these components are not strictly necessary. As long as thereceiver 3700 includes at least one of the above-described components,the user is able to use the multiplexed data obtained throughdemodulation by the demodulator 3702 and error-correcting decoding. Anyreceiver may be freely combined with the above-described componentsaccording to the usage method.

(Multiplexed Data)

The following is a detailed description of a sample configuration ofmultiplexed data. The data configuration typically used in broadcastingis an MPEG-2 transport stream (TS). Therefore the following descriptiondescribes an example related to MPEG2-TS. However, the dataconfiguration of the multiplexed data transmitted by the transmissionand reception methods discussed in the above-described Embodiments isnot limited to MPEG2-TS. The advantageous effects of the above-describedEmbodiments are also achievable using any other data structure.

FIG. 38 illustrates a sample configuration for multiplexed data. Asshown, the multiplexed data are elements making up programmes (orevents, being a portion thereof) currently provided by various services.For example, one or more video streams, audio streams, presentationgraphics (PG) streams, interactive graphics (IG) streams, and other suchelement streams are multiplexed to obtain the multiplexed data. When abroadcast program provided by the multiplexed data is a movie, the videostreams represent main video and sub video of the movie, the audiostreams represent main audio of the movie and sub-audio to be mixed withthe main audio, and the presentation graphics streams representsubtitles for the movie. Main video refers to video images normallypresented on a screen, whereas sub-video refers to video images (forexample, images of text explaining the outline of the movie) to bepresented in a small window inserted within the video images. Theinteractive graphics streams represent an interactive display made up ofGUI (Graphical User Interface) components presented on a screen.

Each stream included in the multiplexed data is identified by anidentifier, termed a PID, uniquely assigned to the stream. For example,PID 0x1011 is assigned to the video stream used for the main video ofthe movie, PIDs 0x1100 through 0x111F are assigned to the audio streams,PIDs 0x1200 through 0x121F are assigned to the presentation graphics,PIDs 0x1400 through 0x141F are assigned to the interactive graphics,PIDs 0x1B00 through 0x1B1F are assigned to the video streams used forthe sub-video of the movie, and PIDs 0x1A00 through 0x1A1F are assignedto the audio streams used as sub-audio to be mixed with the main audioof the movie.

FIG. 39 is a schematic diagram illustrating an example of themultiplexed data being multiplexed. First, a video stream 3901, made upof a plurality of frames, and an audio stream 3904, made up of aplurality of audio frames, are respectively converted into PES packetsequence 3902 and 3905, then further converted into TS packets 3903 and3906. Similarly, a presentation graphics stream 3911 and an interactivegraphics stream 3914 are respectively converted into PES packet sequence3912 and 3915, then further converted into TS packets 3913 and 3916. Themultiplexed data 3917 is made up of the TS packets 3903, 3906, 3913, and3916 multiplexed into a single stream.

FIG. 40 illustrates further details of a PES packet sequence ascontained in the video stream. The first tier of FIG. 40 shows a videoframe sequence in the video stream. The second tier shows a PES packetsequence. Arrows yy1, yy2, yy3, and yy4 indicate the plurality of VideoPresentation Units, which are I-pictures, B-pictures, and P-pictures, inthe video stream as divided and individually stored as the payload of aPES packet. Each PES packet has a PES header. A PES header contains aPTS (Presentation Time Stamp) at which the picture is to be displayed, aDTS (Decoding Time Stamp) at which the picture is to be decoded, and soon.

FIG. 41 illustrates the structure of a TS packet as ultimately writteninto the multiplexed data. A TS packet is a 188-byte fixed-length packetmade up of a 4-byte PID identifying the stream and of a 184-byte TSpayload containing the data. The above-described PES packets are dividedand individually stored as the TS payload. For a BD-ROM, each TS packethas a 4-byte TP_Extra_Header affixed thereto to build a 192-byte sourcepacket, which is to be written as the multiplexed data. TheTP_Extra_Header contains information such as an Arrival_Time_Stamp(ATS). The ATS indicates a time for starring transfer of the TS packetto the PID filter of a decoder. The multiplexed data are made up ofsource packets arranged as indicated in the bottom tier of FIG. 41. ASPN (source packet number) is incremented for each packet, beginning atthe head of the multiplexed data.

In addition to the video streams, audio streams, presentation graphicsstreams, and the like, the TS packets included in the multiplexed dataalso include a PAT (Program Association Table), a PMT (Program MapTable), a PCR (Program Clock Reference) and so on. The PAT indicates thePID of a PMT used in the multiplexed data, and the PID of the PAT itselfis registered as 0. The PMT includes PIDs identifying the respectivestreams, such as video, audio and subtitles, contained in themultiplexed data and attribute information (frame rate, aspect ratio,and the like) of the streams identified by the respective PIDs. Inaddition, the PMT includes various types of descriptors relating to themultiplexed data. One such descriptor may be copy control informationindicating whether or not copying of the multiplexed data is permitted.The PCR includes information for synchronizing the ATC (Arrival TimeClock) serving as the chronological axis of the ATS to the STC (SystemTime Clock) serving as the chronological axis of the PTS and DTS. EachPCR packet includes an STC time corresponding to the ATS at which thepacket is to be transferred to the decoder.

FIG. 42 illustrates the detailed data configuration of a PMT. The PMTstarts with a PMT header indicating the length of the data contained inthe PMT. Following the PMT header, descriptors pertaining to themultiplexed data are arranged. One example of a descriptor included inthe PMT is the copy control information described above. Following thedescriptors, stream information pertaining to the respective streamsincluded in the multiplexed data is arranged. Each piece of streaminformation is composed of stream descriptors indicating a stream typeidentifying a compression codec employed for a corresponding stream, aPID for the stream, and attribute information (frame rate, aspect ratio,and the like) of the stream. The PMT includes the same number of streamdescriptors as the number of streams included in the multiplexed data.

When recorded onto a recoding medium or the like, the multiplexed dataare recorded along with a multiplexed data information file.

FIG. 43 illustrates a sample configuration for the multiplexed datainformation file. As shown, the multiplexed data information file ismanagement information for the multiplexed data, is provided inone-to-one correspondence with the multiplexed data, and is made up ofmultiplexed data information, stream attribute information, and an entrymap.

The multiplexed data information is made up of a system rate, a playbackstart time, and a playback end time. The system rate indicates themaximum transfer rate of the multiplexed data to the PID filter of alater-described system target decoder. The multiplexed data includes ATSat an interval set so as not to exceed the system rate. The playbackstart time is set to the time specified by the PTS of the first videoframe in the multiplexed data, whereas the playback end time is set tothe time calculated by adding the playback duration of one frame to thePTS of the last video frame in the multiplexed data.

FIG. 44 illustrates a sample configuration for the stream attributeinformation included in the multiplexed data information file. As shown,the stream attribute information is attribute information for eachstream included in the multiplexed data, registered for each PID. Thatis, different pieces of attribute information are provided for differentstreams, namely for the video streams, the audio streams, thepresentation graphics streams, and the interactive graphics streams. Thevideo stream attribute information indicates the compression codecemployed to compress the video stream, the resolution of individualpictures constituting the video stream, the aspect ratio, the framerate, and so on. The audio stream attribute information indicates thecompression codec employed to compress the audio stream, the number ofchannels included in the audio stream, the language of the audio stream,the sampling frequency, and so on. This information is used toinitialize the decoder before playback by a player.

In the present Embodiment, the stream type included in the PMT is usedamong the information included in the multiplexed data. When themultiplexed data are recorded on a recording medium, the video streamattribute information included in the multiplexed data information fileis used. Specifically, the video coding method and device described inany of the above Embodiments may be modified to additionally include astep or unit of setting a specific piece of information in the streamtype included in the PMT or in the video stream attribute information.The specific piece of information is for indicating that the video dataare generated by the video coding method and device described in theEmbodiment. According to such a structure, video data generated by thevideo coding method and device described in any of the above Embodimentsis distinguishable from video data compliant with other standards.

FIG. 45 illustrates a sample configuration of an audiovisual outputdevice 4500 that includes a reception device 4504 receiving a modulatedsignal that includes audio and video data transmitted by a broadcaster(base station) or data intended for broadcasting. The configuration ofthe reception device 4504 corresponds to the reception device 3700 fromFIG. 37. The audiovisual output device 4500 incorporates, for example,an OS (Operating System), or incorporates a communication device 4506for connecting to the Internet (e.g., a communication device intendedfor a wireless LAN (Local Area Network) or for Ethernet™). As such, avideo display unit 4501 is able to simultaneously display audio andvideo data, or video in video data for broadcast 4502, and hypertext4503 (from the World Wide Web) provided over the Internet. By operatinga remote control 4507 (alternatively, a mobile phone or keyboard),either of the video in video data for broadcast 4502 and the hypertext4503 provided over the Internet may be selected to change operations.For example, when the hypertext 4503 provided over the Internet isselected, the website displayed may be changed by remote controloperations. When audio and video data, or video in video data forbroadcast 4502 is selected, information from a selected channel(selected (television) program or audio broadcast) may be transmitted bythe remote control 4507. As such, an interface 4505 obtains theinformation transmitted by the remote control. The reception device 4504performs processing such as demodulation and error-correctioncorresponding to the selected channel, thereby obtaining the receiveddata. At this point, the reception device 4504 obtains control symbolinformation that includes information on the transmission method (asdescribed using FIG. 5) from control symbols included the signalcorresponding to the selected channel. As such, the reception device4504 is able to correctly set the reception operations, demodulationscheme, error-correction method and so on, thus enabling the dataincluded in the data symbols transmitted by the broadcaster (basestation) to be obtained. Although the above description is given for anexample of the user using the remote control 4507, the same operationsapply when the user presses a selection key embedded in the audiovisualoutput device 4500 to select a channel.

In addition, the audiovisual output device 4500 may be operated usingthe Internet. For example, the audiovisual output device 4500 may bemade to record (store) a program through another terminal connected tothe Internet. (Accordingly, the audiovisual output device 4500 shouldinclude the drive 3708 from FIG. 37.) The channel is selected beforerecording begins. As such, the reception device 4504 performs processingsuch as demodulation and error-correction corresponding to the selectedchannel, thereby obtaining the received data. At this point, thereception device 4504 obtains control symbol information that includesinformation on the transmission method (the transmission method,modulation scheme, error-correction method, and so on from theabove-described Embodiments) (as described using FIG. 5) from controlsymbols included the signal corresponding to the selected channel. Assuch, the reception device 4504 is able to correctly set the receptionoperations, demodulation scheme, error-correction method and so on, thusenabling the data included in the data symbols transmitted by thebroadcaster (base station) to be obtained.

(Supplement)

The present description considers a communications/broadcasting devicesuch as a broadcaster, a base station, an access point, a terminal, amobile phone, or the like provided with the transmission device, and acommunications device such as a television, radio, terminal, personalcomputer, mobile phone, access point, base station, or the like providedwith the reception device. The transmission device and the receptiondevice pertaining to the present invention are communication devices ina form able to execute applications, such as a television, radio,personal computer, mobile phone, or similar, through connection to somesort of interface (e.g., USB).

Furthermore, in the present Embodiment, symbols other than data symbols,such as pilot symbols (namely preamble, unique word, postamble,reference symbols, scattered pilot symbols and so on), symbols intendedfor control information, and so on may be freely arranged within theframe. Although pilot symbols and symbols intended for controlinformation are presently named, such symbols may be freely namedotherwise as the function thereof remains the important consideration.

Provided that a pilot symbol, for example, is a known symbol modulatedwith PSK modulation in the transmitter and receiver (alternatively, thereceiver may be synchronized such that the receiver knows the symbolstransmitted by the transmitter), the receiver is able to use this symbolfor frequency synchronization, time synchronization, channel estimation(CSI (Channel State Information) estimation for each modulated signal),signal detection, and the like.

The symbols intended for control information are symbols transmittinginformation (such as the modulation scheme, error-correcting codingmethod, coding rate of error-correcting codes, and setting informationfor the top layer used in communications) that is transmitted to thereceiving party in order to execute transmission of non-data (i.e.,applications).

The present invention is not limited to the Embodiments, but may also berealized in various other ways. For example, while the above Embodimentsdescribe communication devices, the present invention is not limited tosuch devices and may be implemented as software for the correspondingcommunications method.

Although the above-described Embodiments describe phase changing methodsfor methods of transmitting two modulated signals from two antennas, nolimitation is intended in this regard. Precoding and a change of phasemay be performed on four signals that have been mapped to generate fourmodulated signals transmitted using four antennas. That is, the presentinvention is applicable to performing a change of phase on N signalsthat have been mapped and precoded to generate N modulated signalstransmitted using N antennas.

Although the above-described Embodiments describe examples of systemswhere two modulated signals are transmitted from two antennas andreceived by two respective antennas in a MIMO communications system, thepresent invention is not limited in this regard and is also applicableto MISO (Multiple Input Single Output) communications systems. In a MISOsystem, the reception device does not include antenna 701_Y, wirelessunit 703_Y, channel fluctuation estimator 707_1 for modulated signal z1,and channel fluctuation estimator 707_2 for modulated signal z2 fromFIG. 7. However, the processing described in Embodiment 1 may still beexecuted to estimate r1 and r2. Technology for receiving and decoding aplurality of signals transmitted simultaneously at a common frequencyare received by a single antenna is widely known. The present inventionis additional processing supplementing conventional technology for asignal processor reverting a phase changed by the transmitter.

Although the present invention describes examples of systems where twomodulated signals are transmitted from two antennas and received by tworespective antennas in a MIMO communications system, the presentinvention is not limited in this regard and is also applicable to MISOsystems. In a MISO system, the transmission device performs precodingand change of phase such that the points described thus far areapplicable. However, the reception device does not include antenna701_Y, wireless unit 703_Y, channel fluctuation estimator 707_1 formodulated signal z1, and channel fluctuation estimator 707_2 formodulated signal z2 from FIG. 7. However, the processing described inthe present description may still be executed to estimate the datatransmitted by the transmission device. Technology for receiving anddecoding a plurality of signals transmitted simultaneously at a commonfrequency are received by a single antenna is widely known (asingle-antenna receiver may apply ML operations (Max-log APP orsimilar)). The present invention may have the signal processor 711 fromFIG. 7 perform demodulation (detection) by taking the precoding andchange of phase applied by the transmitter into consideration.

The present description uses terms such as precoding, precoding weights,precoding matrix, and so on. The terminology itself may be otherwise(e.g., may be alternatively termed a codebook) as the key point of thepresent invention is the signal processing itself.

Furthermore, although the present description discusses examples mainlyusing OFDM as the transmission method, the invention is not limited inthis manner. Multi-carrier methods other than OFDM and single-carriermethods may all be used to achieve similar Embodiments. Here,spread-spectrum communications may also be used. When single-carriermethods are used, the change of phase is performed with respect to thetime domain.

In addition, although the present description discusses the use of MLoperations, APP, Max-log APP, ZF, MMSE and so on by the receptiondevice, these operations may all be generalized as wave detection,demodulation, detection, estimation, and demultiplexing as the softdecision results (log-likelihood and log-likelihood ratio) and the harddecision results (zeroes and ones) obtained thereby are the individualbits of data transmitted by the transmission device.

Different data may be transmitted by each stream s1(t) and s2(t) (s1(i),s2(i)), or identical data may be transmitted thereby.

The two stream baseband signals s1(i) and s2(i) (where i indicatessequence (with respect to time or (carrier) frequency)) undergoprecoding and a regular change of phase (the order of operations may befreely reversed) to generate two post-processing baseband signals z1(i)and z2(i). For post-processing baseband signal z1(i), the in-phasecomponent I is I₁(i) while the quadrature component is Q₁(i), and forpost processing baseband signal z2(i), the in-phase component is I₁(i)while the quadrature component is Q₂(i). The baseband components may beswitched, as long as the following holds.

Let the in-phase component and the quadrature component of switchedbaseband signal r1(i) be I₁(i) and Q₂(i), and the in-phase component andthe quadrature component of switched baseband signal r2(i) be I₂(i) andQ₁(i).The modulated signal corresponding to switched baseband signal r1(i) istransmitted by transmit antenna 1 and the modulated signal correspondingto switched baseband signal r2(i) is transmitted from transmit antenna2, simultaneously on a common frequency. As such, the modulated signalcorresponding to switched baseband signal r1(i) and the modulated signalcorresponding to switched baseband signal r2(i) are transmitted fromdifferent antennas, simultaneously on a common frequency. Alternatively,

-   -   For switched baseband signal r1(i), the in-phase component may        be I₁(i) while the quadrature component may be I₂(i), and for        switched baseband signal r2(i), the in-phase component may be        Q₁(i) while the quadrature component may be Q2(i).    -   For switched baseband signal r1(i), the in-phase component may        be I₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r2(i), the in-phase component may be        Q₁(i) while the quadrature component may be Q2(i).    -   For switched baseband signal r1(i), the in-phase component may        be I₁(i) while the quadrature component may be I₂(i), and for        switched baseband signal r2(i), the in-phase component may be        Q₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r1(i), the in-phase component may        be I₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r2(i), the in-phase component may be        Q₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r1(i), the in-phase component may        be I₁(i) while the quadrature component may be Q₂(i), and for        switched baseband signal r2(i), the in-phase component may be        Q₁(i) while the quadrature component may be I₂(i).    -   For switched baseband signal r1(i), the in-phase component may        be Q₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r2(i), the in-phase component may be        I₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r1(i), the in-phase component may        be Q₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r2(i), the in-phase component may be        Q₁(i) while the quadrature component may be I₂(i).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i) while the quadrature component may be I₂(i), and for        switched baseband signal r1(i), the in-phase component may be        Q₁(i) while the quadrature component may be Q2(i).    -   For switched baseband signal r2(i), the in-phase component may        be I₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r1(i), the in-phase component may be        Q₁(i) while the quadrature component may be Q2(i).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i) while the quadrature component may be I₂(i), and for        switched baseband signal r1(i), the in-phase component may be        Q₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r2(i), the in-phase component may        be I₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r1(i), the in-phase component may be        Q₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i) while the quadrature component may be Q₂(i), and for        switched baseband signal r1(i), the in-phase component may be        I₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i) while the quadrature component may be Q₂(i), and for        switched baseband signal r1(i), the in-phase component may be        Q₁(i) while the quadrature component may be I₂(i).    -   For switched baseband signal r2(i), the in-phase component may        be Q₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r1(i), the in-phase component may be        I₂(i) while the quadrature component may be Q₁(i).    -   For switched baseband signal r2(i), the in-phase component may        be Q₂(i) while the quadrature component may be I₁(i), and for        switched baseband signal r1(i), the in-phase component may be        Q₁(i) while the quadrature component may be I₂(i).

Alternatively, although the above description discusses performing twotypes of signal processing on both stream signals so as to switch thein-phase component and quadrature component of the two signals, theinvention is not limited in this manner. The two types of signalprocessing may be performed on more than two streams, so as to switchthe in-phase component and quadrature component thereof.

Alter, while the above examples describe switching performed on basebandsignals having a common timestamp (common (sub-)carrier) frequency), thebaseband signals being switched need not necessarily have a commontimestamp (common (sub-)carrier) frequency). For example, any of thefollowing are possible.

-   -   For switched baseband signal r1(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r2(i), the in-phase component may        be I₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r1(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r2(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be Q₂(i+w).    -   For switched baseband signal r1(i), the in-phase component may        be I₂(i+v) while the quadrature component may be Q₁(i+w), and        for switched baseband signal r2(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be Q₂(i+w).    -   For switched baseband signal r1(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r2(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r1(i), the in-phase component may        be I₂(i+v) while the quadrature component may be Q₁(i+w), and        for switched baseband signal r2(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r1(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r2(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be I₂(i+w).    -   For switched baseband signal r1(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be I₁(i+v), and        for switched baseband signal r2(i), the in-phase component may        be I₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r1(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be I₁(i+v), and        for switched baseband signal r2(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be I₂(i+w).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r1(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be Q₂(i+w).    -   For switched baseband signal r2(i), the in-phase component may        be I₂(i+v) while the quadrature component may be Q₁(i+w), and        for switched baseband signal r1(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be Q₂(i+w).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r1(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r2(i), the in-phase component may        be I₂(i+v) while the quadrature component may be Q₁(i+w), and        for switched baseband signal r1(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r1(i), the in-phase component may        be I₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r2(i), the in-phase component may        be I₁(i+v) while the quadrature component may be Q₂(i+w), and        for switched baseband signal r1(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be I₂(i+w).    -   For switched baseband signal r2(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be I₁(i+v), and        for switched baseband signal r1(i), the in-phase component may        be I₂(i+w) while the quadrature component may be Q₁(i+v).    -   For switched baseband signal r2(i), the in-phase component may        be Q₂(i+w) while the quadrature component may be I₁(i+v), and        for switched baseband signal r1(i), the in-phase component may        be Q₁(i+v) while the quadrature component may be I₂(i+w).

FIG. 55 illustrates a baseband signal switcher 5502 explaining theabove. As shown, of the two processed baseband signals z1(i) 5501_1 andz2(i) 5501_2, processed baseband signal z1(i) 5501_1 has in-phasecomponent I₁(i) and quadrature component Q₁(i), while processed basebandsignal z2(i) 5501_2 has in-phase component I₂(i) and quadraturecomponent Q₂(i). Then, after switching, switched baseband signal r1(i)5503_1 has in-phase component I_(r1)(i) and quadrature componentQ_(r1)(i), while switched baseband signal r2(i) 5503_2 has in-phasecomponent I_(r2)(i) and quadrature component Q_(r2)(i). The in-phasecomponent I_(r1)(i) and quadrature component Q_(r1)(i) of switchedbaseband signal r1(i) 5503_1 and the in-phase component I_(r2)(i) andquadrature component Q_(r2)(i) of switched baseband signal r2(i) 5503_2may be expressed as any of the above. Although this example describesswitching performed on baseband signals having a common timestamp(common ((sub-)carrier) frequency) and having undergone two types ofsignal processing, the same may be applied to baseband signals havingundergone two types of signal processing but having different timestamps(different ((sub-)carrier) frequencies).

Each of the transmit antennas of the transmission device and each of thereceive antennas of the reception device shown in the figures may beformed by a plurality of antennas.

The present description uses the symbol ∀, which is the universalquantifier, and the symbol ∃, which is the existential quantifier.

Furthermore, the present description uses the radian as the unit ofphase in the complex plane, e.g., for the argument thereof.

When dealing with the complex plane, the coordinates of complex numbersare expressible by way of polar coordinates. For a complex number z=a+jb(where a and b are real numbers and j is the imaginary unit), thecorresponding point (a, b) on the complex plane is expressed with thepolar coordinates [r, θ], converted as follows:

a=r×cos θ

b=r×sin θ

[Math. 49]

r=√{square root over (a ² +b ²)}  (formula 49)

where r is the absolute value of z (r=|z|), and θ is the argumentthereof. As such, z=a+jb is expressible as re^(jθ).

In the present invention, the baseband signals s1, s2, z1, and z2 aredescribed as being complex signals. A complex signal made up of in-phasesignal I and quadrature signal Q is also expressible as complex signalI+jQ. Here, either of I and Q may be equal to zero.

FIG. 46 illustrates a sample broadcasting system using the phasechanging method described in the present description. As shown, a videoencoder 4601 takes video as input, performs video encoding, and outputsencoded video data 4602. An audio encoder 4603 takes audio as input,performs audio encoding, and outputs encoded audio data 4604. A dataencoder 4605 takes data as input, performs data encoding (e.g., datacompression), and outputs encoded data 4606. Taken as a whole, thesecomponents form a source information encoder 4600.

A transmitter 4607 takes the encoded video data 4602, the encoded audiodata 4604, and the encoded data 4606 as input, performs error-correctingcoding, modulation, precoding, and phase changing (e.g., the signalprocessing by the transmission device from FIG. 3) on a subset of or onthe entirety of these, and outputs transmit signals 4608_1 through4608_N. Transmit signals 4608_1 through 4608_N are then transmitted byantennas 4609_1 through 4609_N as radio waves.

A receiver 4612 takes received signals 4611_1 through 4611_M received byantennas 4610_1 through 4610_M as input, performs processing such asfrequency conversion, change of phase, decoding of the precoding,log-likelihood ratio calculation, and error-correcting decoding (e.g.,the processing by the reception device from FIG. 7), and outputsreceived data 4613, 4615, and 4617. A source information decoder 4619takes the received data 4613, 4615, and 4617 as input. A video decoder4614 takes received data 4613 as input, performs video decoding, andoutputs a video signal. The video is then displayed on a televisiondisplay. An audio decoder 4616 takes received data 4615 as input. Theaudio decoder 4616 performs audio decoding and outputs an audio signal.the audio is then played through speakers. A data decoder 4618 takesreceived data 4617 as input, performs data decoding, and outputsinformation.

In the above-described Embodiments pertaining to the present invention,the number of encoders in the transmission device using a multi-carriertransmission method such as OFDM may be any number, as described above.Therefore, as in FIG. 4, for example, the transmission device may haveonly one encoder and apply a method of distributing output to themulti-carrier transmission method such as OFDM. In such circumstances,the wireless units 310A and 310B from FIG. 4 should replace theOFDM-related processors 1301A and 1301B from FIG. 12. The description ofthe OFDM-related processors is as given for Embodiment 1.

Although Embodiment 1 gives Math. 36 (formula 36) as an example of aprecoding matrix, another precoding matrix may also be used, when thefollowing method is applied.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 50} \rbrack & \; \\{\begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix} = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j0} & {\alpha \times ^{j\pi}} \\{\alpha \times ^{j0}} & ^{j0}\end{pmatrix}}} & ( {{formula}\mspace{14mu} 50} )\end{matrix}$

In the precoding matrices of Math. 36 (formula 36) and Math. 50 (formula50), the value of α is set as given by Math. 37 (formula 37) and Math.38 (formula 38). However, no limitation is intended in this manner. Asimple precoding matrix is obtainable by setting α=1, which is also avalid value.

In Embodiment A1, the phase changers from FIGS. 3, 4, 6, 12, 25, 29, 51,and 53 are indicated as having a phase changing value of PHASE[i] (wherei=0, 1, 2, . . . , N−2, N−1 (i being an integer between 0 and N−1)) toachieve a period (cycle) of N (value reached given that FIGS. 3, 4, 6,12, 25, 29, 51, and 53 perform a change of phase on only one basebandsignal). The present description discusses performing a change of phaseon one precoded baseband signal (i.e., in FIGS. 3, 4, 6, 12, 25, 29, 51and 53) namely on precoded baseband signal z2′. Here, PHASE[k] iscalculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 51} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{2k\; \pi}{N}{radians}}} & ( {{formula}\mspace{14mu} 51} )\end{matrix}$

where k=0, 1, 2, . . . , N−2, N−1 (k being an integer between 0 andN−1). When N=5, 7, 9, 11, or 15, the reception device is able to obtaingood data reception quality.

Although the present description discusses the details of phase changingmethods involving two modulated signals transmitted by a plurality ofantennas, no limitation is intended in this regard. Precoding and achange of phase may be performed on three or more baseband signals onwhich mapping has been performed according to a modulation scheme,followed by predetermined processing on the post-phase change basebandsignals and transmission using a plurality of antennas, to realize thesame results.

Programs for executing the above transmission method may, for example,be stored in advance in ROM (Read-Only Memory) and be read out foroperation by a CPU.

Furthermore, the programs for executing the above transmission methodmay be stored on a computer-readable recording medium, the programsstored in the recording medium may be loaded in the RAM (Random AccessMemory) of the computer, and the computer may be operated in accordancewith the programs.

The components of the above-described Embodiments may be typicallyassembled as an LSI (Large Scale Integration), a type of integratedcircuit. Individual components may respectively be made into discretechips, or a subset or entirety of the components may be made into asingle chip. Although an LSI is mentioned above, the terms IC(Integrated Circuit), system LSI, super LSI, or ultra LSI may alsoapply, depending on the degree of integration. Furthermore, the methodof integrated circuit assembly is not limited to LSI. A dedicatedcircuit or a general-purpose processor may be used. After LSI assembly,a FPGA (Field Programmable Gate Array) or reconfigurable processor maybe used.

Furthermore, should progress in the field of semiconductors or emergingtechnologies lead to replacement of LSI with other integrated circuitmethods, then such technology may of course be used to integrate thefunctional blocks. Applications to biotechnology are also plausible.

Embodiment C1

Embodiment 1 explained that the precoding matrix in use may be switchedwhen transmission parameters change. The present Embodiment describes adetailed example of such a case, where, as described above (in thesupplement), the transmission parameters change such that streams s1(t)and s2(t) switch between transmitting different data and transmittingidentical data, and the precoding matrix and phase changing method beingused are switched accordingly.

The example of the present Embodiment describes a situation where twomodulated signals transmitted from two different transmit antennaalternate between having the modulated signals include identical dataand having the modulated signals each include different data.

FIG. 56 illustrates a sample configuration of a transmission deviceswitching between transmission methods, as described above. In FIG. 56,components operating in the manner described for FIG. 54 use identicalreference numbers. As shown, FIG. 56 differs from FIG. 54 in that adistributor 404 takes the frame configuration signal 313 as input. Theoperations of the distributor 404 are described using FIG. 57.

FIG. 57 illustrates the operations of the distributor 404 whentransmitting identical data and when transmitting different data. Asshown, given encoded data x1, x2, x3, x4, x5, x6, and so on, whentransmitting identical data, distributed data 405 is given as x1, x2,x3, x4, x5, x6, and so on, while distributed data 405B is similarlygiven as x1, x2, x3, x4, x5, x6, and so on.

On the other hand, when transmitting different data, distributed data405A are given as x1, x3, x5, x7, x9, and so on, while distributed data405B are given as x2, x4, x6, x8, x10, and so on.

The distributor 404 determines, according to the frame configurationsignal 313 taken as input, whether the transmission mode is identicaldata transmission or different data transmission.

An alternative method to the above is shown in FIG. 58. As shown, whentransmitting identical data, the distributor 404 outputs distributeddata 405A as x1, x2, x3, x4, x5, x6, and so on, while outputting nothingas distributed data 405B. Accordingly, when the frame configurationsignal 313 indicates identical data transmission, the distributor 404operates as described above, while interleaver 304B and mapper 306B fromFIG. 56 do not operate. Thus, only baseband signal 307A output by mapper306A from FIG. 56 is valid, and is taken as input by both weighting unit308A and 308B.

One characteristic feature of the present Embodiment is that, when thetransmission mode switches from identical data transmission to differentdata transmission, the precoding matrix may also be switched. Asindicated by Math. 36 (formula 36) and Math. 39 (formula 39) inEmbodiment 1, given a matrix made up of w11, w12, w21, and w22, theprecoding matrix used to transmit identical data may be as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 52} \rbrack & \; \\{\begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix} = \begin{pmatrix}a & 0 \\0 & a\end{pmatrix}} & ( {{formula}\mspace{14mu} 52} )\end{matrix}$

where a is a real number (a may also be a complex number, but given thatthe baseband signal input as a result of precoding undergoes a change ofphase, a real number is preferable for considerations of circuit sizeand complexity reduction). Also, when a is equal to one, the weightingunits 308A and 308B do not perform weighting and output the input signalas-is.

Accordingly, when transmitting identical data, the weighted basebandsignals 309A and 316B are identical signals output by the weightingunits 308A and 308B.

When the frame configuration signal 313 indicates identical transmissionmode, a phase changer 5201 performs a change of phase on weightedbaseband signal 309A and outputs post-phase change baseband signal 5202.Similarly, when the frame configuration signal indicates identicaltransmission mode, phase changer 317B performs a change of phase onweighted baseband signal 316B and outputs post-phase change basebandsignal 309B. The change of phase performed by phase changer 5201 is ofe^(jA(t)) (alternatively, e^(jA(f)) or e^(jA(t,f))) (where t is time andf is frequency) (accordingly, e^(jA(t)) (alternatively, e^(jA(f)) ore^(jA(t,f))) is the value by which the input baseband signal ismultiplied), and the change of phase performed by phase changer 317B isof e^(jB(t)) (alternatively, e^(jB(f)) or e^(jB(t,f))) (where t is timeand f is frequency) (accordingly, e^(jB(t)) (alternatively, e^(jB(f)) ore^(jB(t,f))) is the value by which the input baseband signal ismultiplied). As such, the following condition is satisfied.

[Math. 53]

Some time t satisfies

e ^(jA(t)) ≠e ^(jB(t))

(Or, some (carrier) frequency f satisfies e^(jA(f))≠e^(jB(f)))

(Or, some (carrier) frequency f and time t satisfye^(jA(t,f))≠e^(jB(t,f)))

As such, the transmit signal is able to reduce multi-path influence andthereby improve data reception quality for the reception device.(However, the change of phase may also be performed by only one of theweighted baseband signals 309A and 316B.)

In FIG. 56, when OFDM is used, processing such as IFFT and frequencyconversion is performed on post-phase change baseband signal 5202, andthe result is transmitted by a transmit antenna. (See FIG. 13)(Accordingly, post-phase change baseband signal 5202 may be consideredthe same as signal 1301A from FIG. 13.) Similarly, when OFDM is used,processing such as IFFT and frequency conversion is performed onpost-phase change baseband signal 309B, and the result is transmitted bya transmit antenna. (See FIG. 13) (Accordingly, post-phase changebaseband signal 309B may be considered the same as signal 1301B fromFIG. 13.)

When the selected transmission mode indicates different datatransmission, then any of Math. 36 (formula 36), Math. 39 (formula 39),and Math. 50 (formula 50) given in Embodiment 1 may apply.Significantly, the phase changers 5201 and 317B from FIG. 56 use adifferent phase changing method than when transmitting identical data.Specifically, as described in Embodiment 1, for example, phase changer5201 performs the change of phase while phase changer 317B does not, orphase changer 317B performs the change of phase while phase changer 5201does not. Only one of the two phase changers performs the change ofphase. As such, the reception device obtains good data reception qualityin the LOS environment as well as the NLOS environment.

When the selected transmission mode indicates different datatransmission, the precoding matrix may be as given in Math. 52 (formula52), or as given in any of Math. 36 (formula 36), Math. 50 (formula 50),and Math. 39 (formula 39), or may be a precoding matrix unlike thatgiven in Math. 52 (formula 52). Thus, the reception device is especiallylikely to experience improvements to data reception quality in the LOSenvironment.

Furthermore, although the present Embodiment discusses examples usingOFDM as the transmission method, the invention is not limited in thismanner. Multi-carrier methods other than OFDM and single-carrier methodsmay all be used to achieve similar Embodiments. Here, spread-spectrumcommunications may also be used. When single-carrier methods are used,the change of phase is performed with respect to the time domain.

As explained in Embodiment 3, when the transmission method involvesdifferent data transmission, the change of phase is carried out on thedata symbols, only. However, as described in the present Embodiment,when the transmission method involves identical data transmission, thenthe change of phase need not be limited to the data symbols but may alsobe performed on pilot symbols, control symbols, and other such symbolsinserted into the transmission frame of the transmit signal. (The changeof phase need not always be performed on symbols such as pilot symbolsand control symbols, though doing so is preferable in order to achievediversity gain.)

Embodiment C2

The present Embodiment describes a configuration method for a basestation corresponding to Embodiment C1.

FIG. 59 illustrates the relationship of a base stations (broadcasters)to terminals. A terminal P (5907) receives transmit signal 5903Atransmitted by antenna 5904A and transmit signal 5905A transmitted byantenna 5906A of broadcaster A (5902A), then performs predeterminedprocessing thereon to obtained received data.

A terminal Q (5908) receives transmit signal 5903A transmitted byantenna 5904A of base station A (5902A) and transmit signal 593Btransmitted by antenna 5904B of base station B (5902B), then performspredetermined processing thereon to obtained received data.

FIGS. 60 and 61 illustrate the frequency allocation of base station A(5902A) for transmit signals 5903A and 5905A transmitted by antennas5904A and 5906A, and the frequency allocation of base station B (5902B)for transmit signals 5903B and 5905B transmitted by antennas 5904B and5906B. In FIGS. 60 and 61, frequency is on the horizontal axis andtransmission power is on the vertical axis.

As shown, transmit signals 5903A and 5905A transmitted by base station A(5902A) and transmit signals 5903B and 5905B transmitted by base stationB (5902B) use at least frequency band X and frequency band Y. Frequencyband X is used to transmit data of a first channel, and frequency band Yis used to transmit data of a second channel.

Accordingly, terminal P (5907) receives transmit signal 5903Atransmitted by antenna 5904A and transmit signal 5905A transmitted byantenna 5906A of base station A (5902A), extracts frequency band Xtherefrom, performs predetermined processing, and thus obtains the dataof the first channel. Terminal Q (5908) receives transmit signal 5903Atransmitted by antenna 5904A of base station A (5902A) and transmitsignal 5903B transmitted by antenna 5904B of base station B (5902B),extracts frequency band Y therefrom, performs predetermined processing,and thus obtains the data of the second channel.

The following describes the configuration and operations of base stationA (5902A) and base station B (5902B).

As described in Embodiment C1, both base station A (5902A) and basestation B (5902B) incorporate a transmission device configured asillustrated by FIGS. 56 and 13. When transmitting as illustrated by FIG.60, base station A (5902A) generates two different modulated signals (onwhich precoding and a change of phase are performed) with respect tofrequency band X as described in Embodiment C1. The two modulatedsignals are respectively transmitted by the antennas 5904A and 5906A.With respect to frequency band Y, base station A (5902A) operatesinterleaver 304A, mapper 306A, weighting unit 308A, and phase changerfrom FIG. 56 to generate modulated signal 5202. Then, a transmit signalcorresponding to modulated signal 5202 is transmitted by antenna 1310Afrom FIG. 13, i.e., by antenna 5904A from FIG. 59. Similarly, basestation B (5902B) operates interleaver 304A, mapper 306A, weighting unit308A, and phase changer 5201 from FIG. 56 to generate modulated signal5202. Then, a transmit signal corresponding to modulated signal 5202 istransmitted by antenna 1310A from FIG. 13, i.e., by antenna 5904B fromFIG. 59.

The creation of encoded data in frequency band Y may involve, as shownin FIG. 56, generating encoded data in individual base stations, or mayinvolve having one of the base stations generate such encoded data fortransmission to other base stations. As an alternative method, one ofthe base stations may generate modulated signals and be configured topass the modulated signals so generated to other base stations.

Also, in FIG. 59, signal 5901 includes information pertaining to thetransmission mode (identical data transmission or different datatransmission). The base stations obtain this signal and thereby switchbetween generation methods for the modulated signals in each frequencyband. Here, signal 5901 is indicated in FIG. 59 as being input fromanother device or from a network. However, configurations where, forexample, base station A (5902) is a master station passing a signalcorresponding to signal 5901 to base station B (5902B) are alsopossible.

As explained above, when the base station transmits different data, theprecoding matrix and phase changing method are set according to thetransmission method to generate modulated signals.

On the other hand, to transmit identical data, two base stationsrespectively generate and transmit modulated signals. In suchcircumstances, base stations each generating modulated signals fortransmission from a common antenna may be considered to be two combinedbase stations using the precoding matrix given by Math. 52 (formula 52).The phase changing method is as explained in Embodiment C1, for example,and satisfies the conditions of Math. 53 (formula 53).

In addition, the transmission method of frequency band X and frequencyband Y may vary over time. Accordingly, as illustrated in FIG. 61, astime passes, the frequency allocation changes from that indicated inFIG. 60 to that indicated in FIG. 61.

According to the present Embodiment, not only can the reception deviceobtain improved data reception quality for identical data transmissionas well as different data transmission, but the transmission devices canalso share a phase changer.

Furthermore, although the present Embodiment discusses examples usingOFDM as the transmission method, the invention is not limited in thismanner. Multi-carrier methods other than OFDM and single-carrier methodsmay all be used to achieve similar Embodiments. Here, spread-spectrumcommunications may also be used. When single-carrier methods are used,the change of phase is performed with respect to the time domain.

As explained in Embodiment 3, when the transmission method involvesdifferent data transmission, the change of phase is carried out on thedata symbols, only. However, as described in the present Embodiment,when the transmission method involves identical data transmission, thenthe change of phase need not be limited to the data symbols but may alsobe performed on pilot symbols, control symbols, and other such symbolsinserted into the transmission frame of the transmit signal. (The changeof phase need not always be performed on symbols such as pilot symbolsand control symbols, though doing so is preferable in order to achievediversity gain.)

Embodiment C3

The present Embodiment describes a configuration method for a repeatercorresponding to Embodiment C1. The repeater may also be termed arepeating station.

FIG. 62 illustrates the relationship of a base stations (broadcasters)to repeaters and terminals. As shown in FIG. 63, base station 6201 atleast transmits modulated signals on frequency band X and frequency bandY. Base station 6201 transmits respective modulated signals on antenna6202A and antenna 6202B. The transmission method here used is describedlater, with reference to FIG. 63.

Repeater A (6203A) performs processing such as demodulation on receivedsignal 6205A received by receive antenna 6204A and on received signal6207A received by receive antenna 6206A, thus obtaining received data.Then, in order to transmit the received data to a terminal, repeater A(6203A) performs transmission processing to generate modulated signals6209A and 6211A for transmission on respective antennas 6210A and 6212A.

Similarly, repeater B (6203B) performs processing such as demodulationon received signal 6205B received by receive antenna 6204B and onreceived signal 6207B received by receive antenna 6206B, thus obtainingreceived data. Then, in order to transmit the received data to aterminal, repeater B (6203B) performs transmission processing togenerate modulated signals 6209B and 6211B for transmission onrespective antennas 6210B and 6212B. Here, repeater B (6203B) is amaster repeater that outputs a control signal 6208. repeater A (6203A)takes the control signal as input. A master repeater is not strictlynecessary. Base station 6201 may also transmit individual controlsignals to repeater A (6203A) and to repeater B (6203B).

Terminal P (5907) receives modulated signals transmitted by repeater A(6203A), thereby obtaining data. Terminal Q (5908) receives signalstransmitted by repeater A (6203A) and by repeater B (6203B), therebyobtaining data. Terminal R (6213) receives modulated signals transmittedby repeater B (6203B), thereby obtaining data.

FIG. 63 illustrates the frequency allocation for a modulated signaltransmitted by antenna 6202A among transmit signals transmitted by thebase station, and the frequency allocation of modulated signalstransmitted by antenna 6202B. In FIG. 63, frequency is on the horizontalaxis and transmission power is on the vertical axis.

As shown, the modulated signals transmitted by antenna 6202A and byantenna 6202B use at least frequency band X and frequency band Y.Frequency band X is used to transmit data of a first channel, andfrequency band Y is used to transmit data of a second channel.

As described in Embodiment C1, the data of the first channel istransmitted using frequency band X in different data transmission mode.Accordingly, as shown in FIG. 63, the modulated signals transmitted byantenna 6202A and by antenna 6202B include components of frequency bandX. These components of frequency band X are received by repeater A andby repeater B. Accordingly, as described in Embodiment 1 and inEmbodiment C1, modulated signals in frequency band X are signals onwhich mapping has been performed, and to which precoding (weighting) andthe change of phase are applied.

As shown in FIG. 62, the data of the second channel is transmitted byantenna 6202A of FIG. 2 and transmits data in components of frequencyband Y. These components of frequency band Y are received by repeater Aand by repeater B.

FIG. 64 illustrate the frequency allocation for transmit signalstransmitted by repeater A and repeater B, specifically for modulatedsignal 6209A transmitted by antenna 6210A and modulated signal 6211Atransmitted by antenna 6212A of repeater 6210A, and for modulated signal6209B transmitted by antenna 6210B and modulated signal 6211Btransmitted by antenna 6212B of repeater B. In FIG. 64, frequency is onthe horizontal axis and transmission power is on the vertical axis.

As shown, modulated signal 6209A transmitted by antenna 6210A andmodulated signal 6211A transmitted by antenna 6212A use at leastfrequency band X and frequency band Y. Also, modulated signal 6209Btransmitted by antenna 6210B and modulated signal 6211B transmitted byantenna 6212B similarly use at least frequency band X and frequency bandY. Frequency band X is used to transmit data of a first channel, andfrequency band Y is used to transmit data of a second channel.

As described in Embodiment C1, the data of the first channel istransmitted using frequency band X in different data transmission mode.Accordingly, as shown in FIG. 64, modulated signal 6209A transmitted byantenna 6210A and modulated signal 6211A transmitted by antenna 6212Binclude components of frequency band X. These components of frequencyband X are received by terminal P. Similarly, as shown in FIG. 64,modulated signal 6209B transmitted by antenna 6210B and modulated signal6211B transmitted by antenna 6212B include components of frequency bandX. These components of frequency band X are received by terminal R.Accordingly, as described in Embodiment 1 and in Embodiment C1,modulated signals in frequency band X are signals on which mapping hasbeen performed, and to which precoding (weighting) and the change ofphase are applied.

As shown in FIG. 64, the data of the second channel is carried by themodulated signals transmitted by antenna 6210A of repeater A (6203A) andby antenna 6210B of repeater B (6203) from FIG. 62 and transmits data incomponents of frequency band Y. Here, the components of frequency band Yin modulated signal 6209A transmitted by antenna 6210A of repeater A(6203A) and those in modulated signal 6209B transmitted by antenna 6210Bof repeater B (6203B) are used in a transmission mode that involvesidentical data transmission, as explained in Embodiment C1. Thesecomponents of frequency band Y are received by terminal Q.

The following describes the configuration of repeater A (6203A) andrepeater B (6203B) from FIG. 62, with reference to FIG. 65.

FIG. 65 illustrates a sample configuration of a receiver and transmitterin a repeater. Components operating identically to those of FIG. 56 usethe same reference numbers thereas. Receiver 6203X takes received signal6502A received by receive antenna 6501A and received signal 6502Breceived by receive antenna 6501B as input, performs signal processing(signal demultiplexing or compositing, error-correction decoding, and soon) on the components of frequency band X thereof to obtain data 6204Xtransmitted by the base station using frequency band X, outputs the datato the distributor 404 and obtains transmission method informationincluded in control information (and transmission method informationwhen transmitted by a repeater), and outputs the frame configurationsignal 313.

Receiver 6203X and onward constitute a processor for generating amodulated signal for transmitting frequency band X. Further, thereceiver here described is not only the receiver for frequency band X asshown in FIG. 65, but also incorporates receivers for other frequencybands. Each receiver forms a processor for generating modulated signalsfor transmitting a respective frequency band.

The overall operations of the distributor 404 are identical to those ofthe distributor in the base station described in Embodiment C2.

When transmitting as indicated in FIG. 64, repeater A (6203A) andrepeater B (6203B) generate two different modulated signals (on whichprecoding and change of phase are performed) in frequency band X asdescribed in Embodiment C1. The two modulated signals are respectivelytransmitted by antennas 6210A and 6212A of repeater A (6203) from FIG.62 and by antennas 6210B and 6212B of repeater B (6203B) from FIG. 62.

As for frequency band Y, repeater A (6203A) operates a processor 6500pertaining to frequency band Y and corresponding to the signal processor6500 pertaining to frequency band X shown in FIG. 65 (the signalprocessor 6500 is the signal processor pertaining to frequency band X,but given that an identical signal processor is incorporated forfrequency band Y, this description uses the same reference numbers),interleaver 304A, mapper 306A, weighting unit 308A, and phase changer5201 to generate modulated signal 5202. A transmit signal correspondingto modulated signal 5202 is then transmitted by antenna 1301A from FIG.13, that is, by antenna 6210A from FIG. 62. Similarly, repeater B (6203B) operates interleaver 304A, mapper 306A, weighting unit 308A, andphase changer 5201 from FIG. 62 pertaining to frequency band Y togenerate modulated signal 5202. Then, a transmit signal corresponding tomodulated signal 5202 is transmitted by antenna 1310A from FIG. 13,i.e., by antenna 6210B from FIG. 62.

As shown in FIG. 66 (FIG. 66 illustrates the frame configuration of themodulated signal transmitted by the base station, with time on thehorizontal axis and frequency on the vertical axis), the base stationtransmits transmission method information 6601, repeater-applied phasechange information 6602, and data symbols 6603. The repeater obtains andapplies the transmission method information 6601, the repeater-appliedphase change information 6602, and the data symbols 6603 to the transmitsignal, thus determining the phase changing method. When therepeater-applied phase change information 6602 from FIG. 66 is notincluded in the signal transmitted by the base station, then as shown inFIG. 62, repeater B (6203B) is the master and indicates the phasechanging method to repeater A (6203A).

As explained above, when the repeater transmits different data, theprecoding matrix and phase changing method are set according to thetransmission method to generate modulated signals.

On the other hand, to transmit identical data, two repeatersrespectively generate and transmit modulated signals. In suchcircumstances, repeaters each generating modulated signals fortransmission from a common antenna may be considered to be two combinedrepeaters using the precoding matrix given by Math. 52 (formula 52). Thephase changing method is as explained in Embodiment C1, for example, andsatisfies the conditions of Math. 53 (formula 53).

Also, as explained in Embodiment C1 for frequency band X, the basestation and repeater may each have two antennas that transmit respectivemodulated signals and two antennas that receive identical data. Theoperations of such a base station or repeater are as described forEmbodiment C1.

According to the present Embodiment, not only can the reception deviceobtain improved data reception quality for identical data transmissionas well as different data transmission, but the transmission devices canalso share a phase changer.

Furthermore, although the present Embodiment discusses examples usingOFDM as the transmission method, the invention is not limited in thismanner. Multi-carrier methods other than OFDM and single-carrier methodsmay all be used to achieve similar Embodiments. Here, spread-spectrumcommunications may also be used. When single-carrier methods are used,the change of phase is performed with respect to the time domain.

As explained in Embodiment 3, when the transmission method involvesdifferent data transmission, the change of phase is carried out on thedata symbols, only. However, as described in the present Embodiment,when the transmission method involves identical data transmission, thenthe change of phase need not be limited to the data symbols but may alsobe performed on pilot symbols, control symbols, and other such symbolsinserted into the transmission frame of the transmit signal. (The changeof phase need not always be performed on symbols such as pilot symbolsand control symbols, though doing so is preferable in order to achievediversity gain.)

Embodiment C4

The present Embodiment concerns a phase changing method different fromthe phase changing methods described in Embodiment 1 and in theSupplement.

In Embodiment 1, Math. 36 (formula 36) is given as an example of aprecoding matrix, and in the Supplement, Math. 50 (formula 50) issimilarly given as another such example. In Embodiment A1, the phasechangers from FIGS. 3, 4, 6, 12, 25, 29, 51, and 53 are indicated ashaving a phase changing value of PHASE[i] (where i=0, 1, 2, . . . , N−2,N−1 (i being an integer between 0 and N−1)) to achieve a period (cycle)of N (value reached given that FIGS. 3, 4, 6, 12, 25, 29, 51, and 53perform a change of phase on only one baseband signal). The presentdescription discusses performing a change of phase on one precodedbaseband signal (i.e., in FIGS. 3, 4, 6, 12, 25, 29, 51 and 53) namelyon precoded baseband signal z2′. Here, PHASE[k] is calculated asfollows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 54} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{k\; \pi}{N}{radians}}} & ( {{formula}\mspace{14mu} 54} )\end{matrix}$

where k=0, 1, 2, . . . , N−2, N−1 (k being an integer between 0 andN−1).

Accordingly, the reception device is able to achieve improvements indata reception quality in the LOS environment, and especially in a radiowave propagation environment. In the LOS environment, when the change ofphase has not been performed, a regular phase relationship occurs.However, when the change of phase is performed, the phase relationshipis modified, in turn avoiding poor conditions in a burst-likepropagation environment. As an alternative to Math. 54 (formula 54),PHASE[k] may be calculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 55} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{k\; \pi}{N}{radians}}} & ( {{formula}\mspace{14mu} 55} )\end{matrix}$

where k=0, 1, 2, . . . , N−2, N−1 (k being an integer between 0 andN−1).

As a further alternative phase changing method, PHASE[k] may becalculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 56} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{k\; \pi}{N} + {Z\mspace{14mu} {radians}}}} & ( {{formula}\mspace{14mu} 56} )\end{matrix}$

where k=0, 1, 2, . . . , N−2, N−1 (k being an integer between 0 andN−1).

As a further alternative phase changing method, PHASE[k] may becalculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 57} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{k\; \pi}{N} + {Z\mspace{14mu} {radians}}}} & ( {{formula}\mspace{14mu} 57} )\end{matrix}$

where k=0, 1, 2, . . . , N−2, N−1 (k being an integer between 0 andN−1).

As such, by performing the change of phase according to the presentEmbodiment, the reception device is made more likely to obtain goodreception quality.

The change of phase of the present Embodiment is applicable not only tosingle-carrier methods but also to multi-carrier methods. Accordingly,the present Embodiment may also be realized using, for example,spread-spectrum communications, OFDM, SC-FDMA, SC-OFDM, wavelet OFDM asdescribed in Non-Patent Literature 7, and so on. As previouslydescribed, while the present Embodiment explains the change of phase asa change of phase with respect to the time domain t, the phase mayalternatively be changed with respect to the frequency domain asdescribed in Embodiment 1. That is, considering the change of phase withrespect to the time domain t described in the present Embodiment andreplacing t with f (f′being the ((sub-) carrier) frequency) leads to achange of phase applicable to the frequency domain. Also, as explainedabove for Embodiment 1, the phase changing method of the presentEmbodiment is also applicable to a change of phase with respect to boththe time domain and the frequency domain. Further, when the phasechanging method described in the present Embodiment satisfies theconditions indicated in Embodiment A1, the reception device is highlylikely to obtain good data quality.

Embodiment C5

The present Embodiment concerns a phase changing method different fromthe phase changing methods described in Embodiment 1, in the Supplement,and in Embodiment C4.

In Embodiment 1, Math. 36 (formula 36) is given as an example of aprecoding matrix, and in the Supplement, Math. 50 (formula 50) issimilarly given as another such example. In Embodiment A1, the phasechangers from FIGS. 3, 4, 6, 12, 25, 29, 51, and 53 are indicated ashaving a phase changing value of PHASE[i] (where i=0, 1, 2, . . . , N−2,N−1 (i being an integer between 0 and N−1)) to achieve a period (cycle)of N (value reached given that FIGS. 3, 4, 6, 12, 25, 29, 51, and 53perform a change of phase on only one baseband signal). The presentdescription discusses performing a change of phase on one precodedbaseband signal (i.e., in FIGS. 3, 4, 6, 12, 25, 29, 51 and 53) namelyon precoded baseband signal z2′.

The characteristic feature of the phase changing method pertaining tothe present Embodiment is the period (cycle) of N=2n+1. To achieve theperiod (cycle) of N=2n+1, n+1 different phase changing values areprepared. Among these n+1 different phase changing values, n phasechanging values are used twice per period (cycle), and one phasechanging value is used only once per period (cycle), thus achieving theperiod (cycle) of N=2n+1. The following describes these phase changingvalues in detail.

The n+1 different phase changing values required to achieve a phasechanging method in which the phase changing value is regularly switchedin a period (cycle) of N=2n+1 are expressed as PHASE[0], PHASE[1],PHASE[i] . . . PHASE[n−1], PHASE[n] (where i=0, 1, 2 . . . n−2, n−1, n(i being an integer between 0 and n)). Here, the n+1 different phasechanging values of PHASE[0], PHASE[1], PHASE[i] . . . PHASE[n−1],PHASE[n] are expressed as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 58} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{2\; k\; \pi}{{2\; n} + 1}{radians}}} & ( {{formula}\mspace{14mu} 58} )\end{matrix}$

where k=0, 1, 2, . . . , n−2, n−1, n (k being an integer between 0 andn). The n+1 different phase changing values PHASE[0], PHASE[1] . . .PHASE[i] . . . PHASE[n−1], PHASE[n] are given by Math. 58 (formula 58).PHASE[0] is used once, while PHASE[1] through PHASE[n] are each usedtwice (i.e., PHASE[1] is used twice, PHASE[2] is used twice, and so on,until PHASE[n−1] is used twice and PHASE[n] is used twice). As such,through this phase changing method in which the phase changing value isregularly switched in a period (cycle) of N=2n+1, a phase changingmethod is realized in which the phase changing value is regularlyswitched between fewer phase changing values. Thus, the reception deviceis able to achieve better data reception quality. As the phase changingvalues are smaller, the effect thereof on the transmission device andreception device may be reduced. According to the above, the receptiondevice is able to achieve improvements in data reception quality in theLOS environment, and especially in a radio wave propagation environment.In the LOS environment, when the change of phase has not been performed,a regular phase relationship occurs. However, when the change of phaseis performed, the phase relationship is modified, in turn avoiding poorconditions in a burst-like propagation environment. As an alternative toMath. 58 (formula 58), PHASE[k] may be calculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 59} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {{- \frac{2\; k\; \pi}{{2\; n} + 1}}{radians}}} & ( {{formula}\mspace{14mu} 59} )\end{matrix}$

where k=0, 1, 2, . . . , n−2, n−1, n (k being an integer between 0 andn).

The n+1 different phase changing values PHASE[0], PHASE[1] . . .PHASE[i] . . . PHASE[n−1], PHASE[n] are given by Math. 59 (formula 59).PHASE[0] is used once, while PHASE[1] through PHASE[n] are each usedtwice (i.e., PHASE[1] is used twice, PHASE[2] is used twice, and so on,until PHASE[n−1] is used twice and PHASE[n] is used twice). As such,through this phase changing method in which the phase changing value isregularly switched in a period (cycle) of N=2n+1, a phase changingmethod is realized in which the phase changing value is regularlyswitched between fewer phase changing values. Thus, the reception deviceis able to achieve better data reception quality. As the phase changingvalues are smaller, the effect thereof on the transmission device andreception device may be reduced.

As a further alternative, PHASE[k] may be calculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 60} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {\frac{2\; k\; \pi}{{2\; n} + 1} + {Z\mspace{20mu} {radians}}}} & ( {{formula}\mspace{14mu} 60} )\end{matrix}$

where k=0, 1, 2, . . . , N−2, N−1 (k being an integer between 0 andN−1).

The n+1 different phase changing values PHASE[0], PHASE[1] . . .PHASE[i] . . . PHASE[n−1], PHASE[n] are given by Math. 60 (formula 60).PHASE[0] is used once, while PHASE[1] through PHASE[n] are each usedtwice (i.e., PHASE[1] is used twice, PHASE[2] is used twice, and so on,until PHASE[n−1] is used twice and PHASE[n] is used twice). As such,through this phase changing method in which the phase changing value isregularly switched in a period (cycle) of N=2n+1, a phase changingmethod is realized in which the phase changing value is regularlyswitched between fewer phase changing values. Thus, the reception deviceis able to achieve better data reception quality. As the phase changingvalues are smaller, the effect thereof on the transmission device andreception device may be reduced.

As a further alternative, PHASE[k] may be calculated as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 61} \rbrack & \; \\{{{PHASE}\lbrack k\rbrack} = {{- \frac{2\; k\; \pi}{{2\; n} + 1}} + {Z\mspace{20mu} {radians}}}} & ( {{formula}\mspace{14mu} 61} )\end{matrix}$

where k=0, 1, 2, . . . , n−2, n−1, n (k being an integer between 0 andn).

The n+1 different phase changing values PHASE[0], PHASE[1] . . .PHASE[i] . . . PHASE[n−1], PHASE[n] are given by Math. 61 (formula 61).PHASE[0] is used once, while PHASE[1] through PHASE[n] are each usedtwice (i.e., PHASE[1] is used twice, PHASE[2] is used twice, and so on,until PHASE[n−1] is used twice and PHASE[n] is used twice). As such,through this phase changing method in which the phase changing value isregularly switched in a period (cycle) of N=2n+1, a phase changingmethod is realized in which the phase changing value is regularlyswitched between fewer phase changing values. Thus, the reception deviceis able to achieve better data reception quality. As the phase changingvalues are smaller, the effect thereof on the transmission device andreception device may be reduced.

As such, by performing the change of phase according to the presentEmbodiment, the reception device is made more likely to obtain goodreception quality.

The change of phase of the present Embodiment is applicable not only tosingle-carrier methods but also to transmission using multi-carriermethods. Accordingly, the present Embodiment may also be realized using,for example, spread-spectrum communications, OFDM, SC-FDMA, SC-OFDM,wavelet OFDM as described in Non-Patent Literature 7, and so on. Aspreviously described, while the present Embodiment explains the changeof phase as a change of phase with respect to the time domain t, thephase may alternatively be changed with respect to the frequency domainas described in Embodiment 1. That is, considering the change of phasewith respect to the time domain t described in the present Embodimentand replacing t with f (f being the ((sub-) carrier) frequency) leads toa change of phase applicable to the frequency domain. Also, as explainedabove for Embodiment 1, the phase changing method of the presentEmbodiment is also applicable to a change of phase with respect to boththe time domain and the frequency domain.

Embodiment C6

The present Embodiment describes a method of regularly changing thephase, specifically that of Embodiment C5, when encoding is performedusing block codes as described in Non-Patent Literature 12 through 15,such as QC LDPC Codes (not only QC-LDPC but also LDPC codes may beused), concatenated LDPC (blocks) and BCH codes, Turbo codes orDuo-Binary Turbo codes using tail-biting, and so on. The followingexample considers a case where two streams s1 and s2 are transmitted.When encoding has been performed using block codes and controlinformation and the like is not necessary, the number of bits making upeach coded block matches the number of bits making up each block code(control information and so on described below may yet be included).When encoding has been performed using block codes or the like andcontrol information or the like (e.g., CRC transmission parameters) isrequired, then the number of bits making up each coded block is the sumof the number of bits making up the block codes and the number of bitsmaking up the information.

FIG. 34 illustrates the varying numbers of symbols and slots needed ineach coded block when block codes are used. FIG. 34 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 4, and thetransmission device has only one encoder. (Here, the transmission methodmay be any single-carrier method or multi-carrier method such as OFDM.)

As shown in FIG. 34, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

Then, given that the transmission device from FIG. 4 transmits twostreams simultaneously, 1500 of the aforementioned 3000 symbols neededwhen the modulation scheme is QPSK are assigned to s1 and the other 1500symbols are assigned to s2. As such, 1500 slots for transmitting the1500 symbols (hereinafter, slots) are required for each of s1 and s2.

By the same reasoning, when the modulation scheme is 16-QAM, 750 slotsare needed to transmit all of the bits making up each coded block, andwhen the modulation scheme is 64-QAM, 500 slots are needed to transmitall of the bits making up each coded block.

The following describes the relationship between the above-defined slotsand the phase, as pertains to methods for a regular change of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase, which has a period (cycle) of five. That is, the phasechanger of the transmission device from FIG. 4 uses five phase changingvalues (or phase changing sets) to achieve the period (cycle) of five.However, as described in Embodiment C5, three different phase changingvalues are present. Accordingly, some of the five phase changing valuesneeded for the period (cycle) of five are identical. (As in FIG. 6, fivephase changing values are needed in order to perform a change of phasehaving a period (cycle) of five on precoded baseband signal z2′ only.Also, as in FIG. 26, two phase changing values are needed for each slotin order to perform the change of phase on both precoded basebandsignals z1′ and z2′. These two phase changing values are termed a phasechanging set. Accordingly, five phase changing sets should ideally beprepared in order to perform a change of phase having a period (cycle)of five in such circumstances). The five phase changing values (or phasechanging sets) needed for the period (cycle) of five are expressed asP[0], P[1], P[2], P[3], and P[4].

The following describes the relationship between the above-defined slotsand the phase, as pertains to methods for a regular change of phase.

For the above-described 1500 slots needed to transmit the 6000 bitsmaking up a single coded block when the modulation scheme is QPSK, phasechanging value P[0] is used on 300 slots, phase changing value P[1] isused on 300 slots, phase changing value P[2] is used on 300 slots, phasechanging value P[3] is used on 300 slots, and phase changing value P[4]is used on 300 slots. This is due to the fact that any bias in phasechanging value usage causes great influence to be exerted by the morefrequently used phase changing value, and that the reception device isdependent on such influence for data reception quality.

Similarly, for the above-described 1500 slots needed to transmit the6000 bits making up the pair of coded blocks when the modulation schemeis 16-QAM, phase changing value P[0] is used on 150 slots, phasechanging value P[1] is used on 150 slots, phase changing value P[2] isused on 150 slots, phase changing value P[3] is used on 150 slots, andphase changing value P[4] is used on 150 slots.

Further, for the above-described 500 slots needed to transmit the 6000bits making up a single coded block when the modulation scheme is64-QAM, phase changing value P[0] is used on 100 slots, phase changingvalue P[1] is used on 100 slots, phase changing value P[2] is used on100 slots, phase changing value P[3] is used on 100 slots, and phasechanging value P[4] is used on 100 slots.

As described above, a phase changing method for regularly varying thephase changing value as given in Embodiment C5 requires the preparationof N=2n+1 phase changing values P[0], P[1] . . . P[2n−1], P[2n] (whereP[0], P[1] . . . P[2n−1], P[2n] are expressed as PHASE[0], PHASE[1],PHASE[2] PHASE[n−1], PHASE[n] (see Embodiment C5)). As such, in order totransmit all of the bits making up the coded block, phase changing valueP[0] is used on K₀ slots, phase changing value P[1] is used on K₁ slots,phase changing value P[i] is used on Ki slots (where i=0, 1, 2, . . . ,2n−1, 2n (i being an integer between 0 and 2n)), and phase changingvalue P[2n] is used on K₂ slots, such that Condition #C01 is met.

(Condition #C01)

K₀=K₁ . . . =K_(i)= . . . K_(2n). That is, K_(a)=K_(b) (∀a and ∀b wherea, b,=0, 1, 2 . . . 2n−1, 2n (a and b being integers between 0 and 2n),a≠b).

A phase changing method for a regular change of phase changing value asgiven in Embodiment C5 having a period (cycle) of N=2n+1 requires thepreparation of phase changing values PHASE[0], PHASE[1], PHASE[2] . . .PHASE[n−1], PHASE[n]. As such, in order to transmit all of the bitsmaking up a single coded block, phase changing value PHASE[0] is used onG₀ slots, phase changing value PHASE[1] is used on G₁ slots, phasechanging value PHASE[i] is used on G_(i) slots (where i=0, 1, 2, . . . ,n−1, n (i being an integer between 0 and n)), and phase changing valuePHASE[n] is used on G_(n) slots, such that Condition #C01 is met.Condition #C01 may be modified as follows.

(Condition #C02)

2×G₀=G₁ . . . =G_(i)= . . . G_(n). That is, 2×G₀=G_(a) (∀a where a=1, 2. . . n−1, n (a being an integer between 1 and n).

Then, when a communication system that supports multiple modulationschemes selects one such supported method for use, Condition #C01 (orCondition #C02) is met for the supported modulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #C01 (or Condition #C02) may not be satisfied for somemodulation schemes. In such a case, the following condition appliesinstead of Condition #C01.

(Condition #C03)

The difference between K_(a) and K_(b) satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . 2n−1,2n (a and b being integers between 0 and 2n), a≠b).

Alternatively, Condition #C03 may be expressed as follows.

(Condition #C04)

The difference between G_(a) and G_(b) satisfies 0, 1, or 2. That is,|G_(a)−G_(b)| satisfies 0, 1, or 2 (∀a, ∀b, where a, b=1, 2 . . . n−1, n(a and b being integers between 1 and n), a≠b)andThe difference between 2×G₀ and G_(a) satisfies 0, 1, or 2. That is,|2×G₀−G_(a)| satisfies 0, 1, or 2 (∀a, where a=1, 2 . . . n−1, n (abeing an integer between 1 and n)).

FIG. 35 illustrates the varying numbers of symbols and slots needed intwo coded blocks when block codes are used. FIG. 35 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 3 and FIG.12, and the transmission device has two encoders. (Here, thetransmission method may be any single-carrier method or multi-carriermethod such as OFDM.)

As shown in FIG. 35, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

The transmission device from FIG. 3 and the transmission device fromFIG. 12 each transmit two streams at once, and have two encoders. Assuch, the two streams each transmit different code blocks. Accordingly,when the modulation scheme is QPSK, two coded blocks drawn from s1 ands2 are transmitted within the same interval, e.g., a first coded blockdrawn from s1 is transmitted, then a second coded block drawn from s2 istransmitted. As such, 3000 slots are needed in order to transmit thefirst and second coded blocks.

By the same reasoning, when the modulation scheme is 16-QAM, 1500 slotsare needed to transmit all of the bits making up two coded blocks, andwhen the modulation scheme is 64-QAM, 1000 slots are needed to transmitall of the bits making up the two coded blocks.

The following describes the relationship between the above-defined slotsand the phase, as pertains to methods for a regular change of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase, which has a period (cycle) of five. That is, the phasechanger of the transmission device from FIG. 4 uses five phase changingvalues (or phase changing sets) to achieve the period (cycle) of five.However, as described in Embodiment C5, three different phase changingvalues are present. Accordingly, some of the five phase changing valuesneeded for the period (cycle) of five are identical. (As in FIG. 6, fivephase changing values are needed in order to perform a change of phasehaving a period (cycle) of five on precoded baseband signal z2′ only.Also, as in FIG. 26, two phase changing values are needed for each slotin order to perform the change of phase on both precoded basebandsignals z1′ and z2′. These two phase changing values are termed a phasechanging set. Accordingly, five phase changing sets should ideally beprepared in order to perform a change of phase having a period (cycle)of five in such circumstances). The five phase changing values (or phasechanging sets) needed for the period (cycle) of five are expressed asP[0], P[1], P[2], P[3], and P[4].

For the above-described 3000 slots needed to transmit the 6000×2 bitsmaking up the pair of coded blocks when the modulation scheme is QPSK,phase changing value P[0] is used on 600 slots, phase changing valueP[1] is used on 600 slots, phase changing value P[2] is used on 600slots, phase changing value P[3] is used on 600 slots, and phasechanging value P[4] is used on 600 slots. This is due to the fact thatany bias in phase changing value usage causes great influence to beexerted by the more frequently used phase changing value, and that thereception device is dependent on such influence for data receptionquality.

Further, in order to transmit the first coded block, phase changingvalue P[0] is used on slots 600 times, phase changing value P[1] is usedon slots 600 times, phase changing value P[2] is used on slots 600times, phase changing value P[3] is used on slots 600 times, and phasechanging value PHASE[4] is used on slots 600 times. Furthermore, inorder to transmit the second coded block, phase changing value P[0] isused on slots 600 times, phase changing value P[1] is used on slots 600times, phase changing value P[2] is used on slots 600 times, phasechanging value P[3] is used on slots 600 times, and phase changing valueP[4] is used on slots 600 times.

Similarly, for the above-described 1500 slots needed to transmit the6000×2 bits making up the pair of coded blocks when the modulationscheme is 16-QAM, phase changing value P[0] is used on 300 slots, phasechanging value P[1] is used on 300 slots, phase changing value P[2] isused on 300 slots, phase changing value P[3] is used on 300 slots, andphase changing value P[4] is used on 300 slots.

Furthermore, in order to transmit the first coded block, phase changingvalue P[0] is used on slots 300 times, phase changing value P[1] is usedon slots 300 times, phase changing value P[2] is used on slots 300times, phase changing value P[3] is used on slots 300 times, and phasechanging value P[4] is used on slots 300 times. Furthermore, in order totransmit the second coded block, phase changing value P[0] is used onslots 300 times, phase changing value P[1] is used on slots 300 times,phase changing value P[2] is used on slots 300 times, phase changingvalue P[3] is used on slots 300 times, and phase changing value P[4] isused on slots 300 times.

Similarly, for the above-described 1000 slots needed to transmit the6000×2 bits making up the pair of coded blocks when the modulationscheme is 64-QAM, phase changing value P[0] is used on 200 slots, phasechanging value P[1] is used on 200 slots, phase changing value P[2] isused on 200 slots, phase changing value P[3] is used on 200 slots, andphase changing value P[4] is used on 200 slots.

Furthermore, in order to transmit the first coded block, phase changingvalue P[0] is used on slots 200 times, phase changing value P[1] is usedon slots 200 times, phase changing value P[2] is used on slots 200times, phase changing value P[3] is used on slots 200 times, and phasechanging value P[4] is used on slots 200 times. Furthermore, in order totransmit the second coded block, phase changing value P[0] is used onslots 200 times, phase changing value P[1] is used on slots 200 times,phase changing value P[2] is used on slots 200 times, phase changingvalue P[3] is used on slots 200 times, and phase changing value P[4] isused on slots 200 times.

As described above, a phase changing method for regularly varying thephase changing value as given in Embodiment C5 requires the preparationof N=2n+1 phase changing values P[0], P[1] . . . P[2n−1], P[2n] (whereP[0], P[1] . . . P[2n−1], P[2n] are expressed as PHASE[0], PHASE[1],PHASE[2] . . . PHASE[n−1], PHASE[n] (see Embodiment C5)). As such, inorder to transmit all of the bits making up the two coded blocks, phasechanging value P[0] is used on K₀ slots, phase changing value P[1] isused on K₁ slots, phase changing value P[i] is used on K_(i) slots(where i=0, 1, 2 . . . 2n−1, 2n (i being an integer between 0 and 2n)),and phase changing value P[2n] is used on K2n slots.

(Condition #C05)

K₀=K₁ . . . =K_(i)= . . . K_(2n). That is, K_(a)=K_(b) (∀a and ∀b wherea, b,=0, 1, 2 . . . 2n−1, 2n (a and b being integers between 0 and 2n,a≠b).

In order to transmit all of the bits making up the first coded block,phase changing value P[0] is used K_(0,1) times, phase changing valueP[1] is used K₁₁ times, phase changing value P[i] is used K_(i,1) (wherei=0, 1, 2 . . . 2n−1, 2n (i being an integer between 0 and 2n)), andphase changing value P[2n] is used K_(2n,1) times.

(Condition #C06)

K_(0,1)=K_(1,1) . . . =K_(i,1)= . . . K_(2n,1). That is, K_(a,1)=K_(b,1)(∀a and ∀b where a, b,=0, 1, 2 . . . 2n−1, 2n (a and b being integersbetween 0 and 2n), a≠b).

In order to transmit all of the bits making up the second coded block,phase changing value P[0] is used K_(0,2) times, phase changing valueP[1] is used K_(1,2) times, phase changing value P[i] is used K_(i,2)(where i=0, 1, 2 . . . 2n−1, 2n (i being an integer between 0 and 2n)),and phase changing value P[2n] is used K_(2n,2) times.

(Condition #C07)

K_(0,2)=K_(1,2) . . . =K_(i,2)= . . . K_(2n,2). That is, K_(a,2)=K_(b,2)(∀a and ∀b where a, b,=0, 1, 2 . . . 2n−1, 2n (a and b being integersbetween 0 and 2n), a≠b).

A phase changing method for regularly varying the phase changing valueas given in Embodiment C5 having a period (cycle) of N=2n+1 requires thepreparation of phase changing values PHASE[0], PHASE[1], PHASE[2] . . .PHASE[n−1], PHASE[n]. As such, in order to transmit all of the bitsmaking up the two coded blocks, phase changing value PHASE[0] is used onG₀ slots, phase changing value PHASE[1] is used on G₁ slots, phasechanging value PHASE[i] is used on G_(i) slots (where i=0, 1, 2 . . .n−1, n (i being an integer between 0 and n)), and phase changing valuePHASE[n] is used on G_(n) slots, such that Condition #C05 is met.

(Condition #C08)

2×G₀=G₁ . . . =G_(i)= . . . G_(n). That is, 2×G₀=G_(a) (∀a where a=1, 2. . . n−1, n (a being an integer between 1 and n)).

In order to transmit all of the bits making up the first coded block,phase changing value PHASE[0] is used G_(0,1) times, phase changingvalue PHASE[1] is used G_(1,1) times, phase changing value PHASE[i] isused G_(i,1) (where i=0, 1, 2 . . . n−1, n being an integer between 0and n)), and phase changing value PHASE[n] is used G_(n,1) times.

(Condition #C09)

2×G_(0,1)=G_(1,1) . . . =G_(i,1)= . . . G_(n,1). That is,2×G_(0,1)=G_(a,1) (∀a where a=1, 2 . . . n−1, n (a being an integerbetween 1 and n)).In order to transmit all of the bits making up the second coded block,phase changing value PHASE[0] is used G_(0,2) times, phase changingvalue PHASE[1] is used G_(1,2) times, phase changing value PHASE[i] isused G_(1,2) (where i=0, 1, 2 . . . n−1, n being an integer between 0and n)), and phase changing value PHASE[n] is used G_(n,1) times.

(Condition #C10)

2×G_(0,2)=G_(1,2) . . . =G_(n,2)=G_(n,2). That is, 2×G_(0,2)=G_(a,2) (∀awhere a=1, 2 . . . n−1, n (a being an integer between 1 and n)).

Then, when a communication system that supports multiple modulationschemes selects one such supported method for use, Condition #C05,Condition #C06, and Condition #C07 (or Condition #C08, Condition #C09,and Condition #C10) is met for the supported modulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #C05, Condition #C06, and Condition #C07 (or Condition #C08,Condition #C09, and Condition #C10) may not be satisfied for somemodulation schemes. In such a case, the following conditions applyinstead of Condition #C05, Condition #C06, and Condition #C07.

(Condition #C11)

The difference between K_(a) and K_(b) satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . 2n−1,2n (a and b being integers between 0 and 2n), a≠b).

(Condition #C12)

The difference between K_(a,1) and K_(b,1), satisfies 0 or 1. That is,|K_(a,1)−K_(b,1)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . .2n−1, 2n (a and b being integers between 0 and 2n), a≠b).

(Condition #C13)

The difference between K_(a,2) and K_(b,2) satisfies 0 or 1. That is,|K_(a,2)−K_(b,2)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . .2n−1, 2n (a and b being integers between 0 and 2n), a≠b).Alternatively, Condition #C11, Condition #C12, and Condition #C13 may beexpressed as follows.

(Condition #C14)

The difference between G_(a) and G_(b) satisfies 0, 1, or 2. That is,|G_(a)−G_(b)| satisfies 0, 1, or 2 (∀a, ∀b, where a, b=1, 2 . . . n−1, n(a and b being integers between 1 and n), a≠b)andThe difference between 2×G₀ and G_(a) satisfies 0, 1, or 2. That is,|2×G₀−G_(a)| satisfies 0, 1, or 2 (∀a, where a=1, 2 . . . n−1, n (abeing an integer between 1 and n)).

(Condition #C15)

The difference between G_(a,1) and G_(b,1) satisfies 0, 1, or 2. Thatis, |G_(a,1)−G_(b,1)| satisfies 0, 1, or 2 (∀a, ∀b, where a, b=1, 2 . .. n−1, n (a and b being integers between 1 and n), a≠b)andThe difference between 2×G_(0,1) and G_(a,1) satisfies 0, 1, or 2. Thatis, |2×G_(0,1)−G_(a,1)| satisfies 0, 1, or 2 (∀a, where a=1, 2 . . .n−1, n (a being an integer between 1 and n))

(Condition #C16)

The difference between G_(a,2) and G_(b,)2 satisfies 0, 1, or 2. Thatis, |G_(a,2)−G_(b,2)| satisfies 0, 1, or 2 (∀a, ∀b, where a, b=1, 2 . .. n−1, n (a and b being integers between 1 and n), a≠b)andThe difference between 2×G_(0,2) and G_(a,2) satisfies 0, 1, or 2. Thatis, |2×G_(0,2)−G_(a,2)| satisfies 0, 1, or 2 (∀a, where a=1, 2 . . .n−1, n (a being an integer between 1 and n))

As described above, bias among the phase changing values being used totransmit the coded blocks is removed by creating a relationship betweenthe coded block and the phase changing values. As such, data receptionquality can be improved for the reception device.

In the present Embodiment, N phase changing values (or phase changingsets) are needed in order to perform a change of phase having a period(cycle) of N with the method for a regular change of phase. As such, Nphase changing values (or phase changing sets) P[0], P[1], P[2] . . .P[N−2], and P[N−1] are prepared. However, schemes exist for ordering thephases in the stated order with respect to the frequency domain. Nolimitation is intended in this regard. The N phase changing values (orphase changing sets) P[0], P[1], P[2] . . . P[N−2], and P[N−1] may alsochange the phases of blocks in the time domain or in the time-frequencydomain to obtain a symbol arrangement as described in Embodiment 1.Although the above examples discuss a phase changing scheme with aperiod (cycle) of N, the same effects are obtainable using N phasechanging values (or phase changing sets) at random. That is, the N phasechanging values (or phase changing sets) need not always have regularperiodicity. As long as the above-described conditions are satisfied,quality data reception improvements are realizable for the receptiondevice.

Furthermore, given the existence of modes for spatial multiplexing MIMOmethods, MIMO methods using a fixed precoding matrix, space-time blockcoding methods, single-stream transmission, and methods using a regularchange of phase, the transmission device (broadcaster, base station) mayselect any one of these transmission methods.

As described in Non-Patent Literature 3, spatial multiplexing MIMOmethods involve transmitting signals s1 and s2, which are mapped using aselected modulation scheme, on each of two different antennas. MIMOmethods using a fixed precoding matrix involve performing precoding only(with no change in phase). Further, space-time block coding methods aredescribed in Non-Patent Literature 9, 16, and 17. Single-streamtransmission methods involve transmitting signal s1, mapped with aselected modulation scheme, from an antenna after performingpredetermined processing.

Schemes using multi-carrier transmission such as OFDM involve a firstcarrier group made up of a plurality of carriers and a second carriergroup made up of a plurality of carriers different from the firstcarrier group, and so on, such that multi-carrier transmission isrealized with a plurality of carrier groups. For each carrier group, anyof spatial multiplexing MIMO schemes, MIMO schemes using a fixedprecoding matrix, space-time block coding schemes, single-streamtransmission, and schemes using a regular change of phase may be used.In particular, schemes using a regular change of phase on a selected(sub-)carrier group are preferably used to realize the presentEmbodiment.

When a change of phase by, for example, a phase changing value for P[i]of X radians is performed on only one precoded baseband signal, thephase changers of FIGS. 3, 4, 6, 12, 25, 29, 51, and 53 multiplyprecoded baseband signal z2′ by e^(jX). Then, when a change of phase by,for example, a phase changing set for P[i] of X radians and Y radians isperformed on both precoded baseband signals, the phase changers fromFIGS. 26, 27, 28, 52, and 54 multiply precoded baseband signal z2′ bye^(jX) and multiply precoded baseband signal z1′ by e^(jY).

Embodiment C7

The present Embodiment describes a method of regularly changing thephase, specifically as done in Embodiment A1 and Embodiment C6, whenencoding is performed using block codes as described in Non-PatentLiterature 12 through 15, such as QC LDPC Codes (not only QC-LDPC butalso LDPC (block) codes may be used), concatenated LDPC and BCH codes,Turbo codes or Duo-Binary Turbo codes, and so on. The following exampleconsiders a case where two streams s1 and s2 are transmitted. Whenencoding has been performed using block codes and control informationand the like is not necessary, the number of bits making up each codedblock matches the number of bits making up each block code (controlinformation and so on described below may yet be included). Whenencoding has been performed using block codes or the like and controlinformation or the like (e.g., CRC transmission parameters) is required,then the number of bits making up each coded block is the sum of thenumber of bits making up the block codes and the number of bits makingup the information.

FIG. 34 illustrates the varying numbers of symbols and slots needed inone coded block when block codes are used. FIG. 34 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 4, and thetransmission device has only one encoder. (Here, the transmission methodmay be any single-carrier method or multi-carrier method such as OFDM.)

As shown in FIG. 34, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

Then, given that the transmission device from FIG. 4 transmits twostreams simultaneously, 1500 of the aforementioned 3000 symbols neededwhen the modulation scheme is QPSK are assigned to s1 and the other 1500symbols are assigned to s2. As such, 1500 slots for transmitting the1500 symbols (hereinafter, slots) are required for each of s1 and s2.

By the same reasoning, when the modulation scheme is 16-QAM, 750 slotsare needed to transmit all of the bits making up two coded blocks, andwhen the modulation scheme is 64-QAM, 500 slots are needed to transmitall of the bits making up the two coded blocks.

The following describes the relationship between the above-defined slotsand the phase, as pertains to methods for a regular change of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase, which has a period (cycle) of five. The phase changingvalues (or phase changing sets) prepared in order to regularly changethe phase with a period (cycle) of five are P[0], P[1], P[2], P[3], andP[4]. However, P[0], P[1], P[2], P[3], and P[4] should include at leasttwo different phase changing values (i.e., P[0], P[1], P[2], P[3], andP[4] may include identical phase changing values). (As in FIG. 6, fivephase changing values are needed in order to perform a change of phasehaving a period (cycle) of five on precoded baseband signal z2′ only.Also, as in FIG. 26, two phase changing values are needed for each slotin order to perform the change of phase on both precoded basebandsignals z1′ and z2′. These two phase changing values are termed a phasechanging set. Accordingly, five phase changing sets should ideally beprepared in order to perform a change of phase having a period (cycle)of five in such circumstances).

For the above-described 1500 slots needed to transmit the 6000 bitsmaking up a single coded block when the modulation scheme is QPSK, phasechanging value P[0] is used on 300 slots, phase changing value P[1] isused on 300 slots, phase changing value P[2] is used on 300 slots, phasechanging value P[3] is used on 300 slots, and phase changing value P[4]is used on 300 slots. This is due to the fact that any bias in phasechanging value usage causes great influence to be exerted by the morefrequently used phase changing value, and that the reception device isdependent on such influence for data reception quality.

Further, for the above-described 750 slots needed to transmit the 6000bits making up a single coded block when the modulation scheme is16-QAM, phase changing value P[0] is used on 150 slots, phase changingvalue P[1] is used on 150 slots, phase changing value P[2] is used on150 slots, phase changing value P[3] is used on 150 slots, and phasechanging value P[4] is used on 150 slots.

Further, for the above-described 500 slots needed to transmit the 6000bits making up a single coded block when the modulation scheme is64-QAM, phase changing value P[0] is used on 100 slots, phase changingvalue P[1] is used on 100 slots, phase changing value P[2] is used on100 slots, phase changing value P[3] is used on 100 slots, and phasechanging value P[4] is used on 100 slots.

As described above, the phase changing values used in the phase changingmethod regularly switching between phase changing values with a period(cycle) of N are expressed as P[0], P[1] . . . P[N−2], P[N−1]. However,P[0], P[1] . . . P[N−2], P[N−1] should include at least two differentphase changing values (i.e., P[0], P[1] . . . P[N−2], P[N−1] may includeidentical phase changing values). In order to transmit all of the bitsmaking up a single coded block, phase changing value P[0] is used on K₀slots, phase changing value P[1] is used on K₁ slots, phase changingvalue P[i] is used on K_(i) slots (where i=0, 1, 2 . . . N−1 (i being aninteger between 0 and N−1)), and phase changing value P[N−1] is used onK_(N−1) slots, such that Condition #C17 is met.

(Condition #C17)

K₀=K₁ . . . =K_(i)= . . . K_(N−1). That is, K_(a)=K_(b) (∀a and ∀b wherea, b,=0, 1, 2 . . . N−1 (a and b being integers between 0 and N−1),a≠b).

Then, when a communication system that supports multiple modulationschemes selects one such supported method for use, Condition #C17 is metfor the supported modulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #C17 may not be satisfied for some modulation schemes. In sucha case, the following condition applies instead of Condition #C17.

(Condition #C18)

The difference between K_(a) and K_(b) satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (aand b being integers between 0 and N−1), a≠b).

FIG. 35 illustrates the varying numbers of symbols and slots needed intwo coded blocks when block codes are used. FIG. 35 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 3 and FIG.12, and the transmission device has two encoders. (Here, thetransmission method may be any single-carrier method or multi-carriermethod such as OFDM.)

As shown in FIG. 35, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

The transmission device from FIG. 3 and the transmission device fromFIG. 12 each transmit two streams at once, and have two encoders. Assuch, the two streams each transmit different code blocks. Accordingly,when the modulation scheme is QPSK, two coded blocks drawn from s1 ands2 are transmitted within the same interval, e.g., a first coded blockdrawn from s1 is transmitted, then a second coded block drawn from s2 istransmitted. As such, 3000 slots are needed in order to transmit thefirst and second coded blocks.

By the same reasoning, when the modulation scheme is 16-QAM, 1500 slotsare needed to transmit all of the bits making up two coded blocks, andwhen the modulation scheme is 64-QAM, 1000 slots are needed to transmitall of the bits making up the two coded blocks.

The following describes the relationship between the above-defined slotsand the phase, as pertains to methods for a regular change of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase, which has a period (cycle) of five. That is, the phasechanger of the transmission device from FIG. 4 uses five phase changingvalues (or phase changing sets) P[0], P[1], P[2], P[3], and P[4] toachieve the period (cycle) of five. However, P[0], P[1], P[2], P[3], andP[4] should include at least two different phase changing values (i.e.,P[0], P[1], P[2], P[3], and P[4] may include identical phase changingvalues). (As in FIG. 6, five phase changing values are needed in orderto perform a change of phase having a period (cycle) of five on precodedbaseband signal z2′ only. Also, as in FIG. 26, two phase changing valuesare needed for each slot in order to perform the change of phase on bothprecoded baseband signals z1′ and z2′. These two phase changing valuesare termed a phase changing set. Accordingly, five phase changing setsshould ideally be prepared in order to perform a change of phase havinga period (cycle) of five in such circumstances). The five phase changingvalues (or phase changing sets) needed for the period (cycle) of fiveare expressed as P[0], P[1], P[2], P[3], and P[4].

For the above-described 3000 slots needed to transmit the 6000×2 bitsmaking up the pair of coded blocks when the modulation scheme is QPSK,phase changing value P[0] is used on 600 slots, phase changing valueP[1] is used on 600 slots, phase changing value P[2] is used on 600slots, phase changing value P[3] is used on 600 slots, and phasechanging value P[4] is used on 600 slots. This is due to the fact thatany bias in phase changing value usage causes great influence to beexerted by the more frequently used phase changing value, and that thereception device is dependent on such influence for data receptionquality.

Further, in order to transmit the first coded block, phase changingvalue P[0] is used on slots 600 times, phase changing value P[1] is usedon slots 600 times, phase changing value P[2] is used on slots 600times, phase changing value P[3] is used on slots 600 times, and phasechanging value PHASE[4] is used on slots 600 times. Furthermore, inorder to transmit the second coded block, phase changing value P[0] isused on slots 600 times, phase changing value P[1] is used on slots 600times, phase changing value P[2] is used on slots 600 times, phasechanging value P[3] is used on slots 600 times, and phase changing valueP[4] is used on slots 600 times.

Similarly, for the above-described 1500 slots needed to transmit the6000×2 bits making up the pair of coded blocks when the modulationscheme is 16-QAM, phase changing value P[0] is used on 300 slots, phasechanging value P[1] is used on 300 slots, phase changing value P[2] isused on 300 slots, phase changing value P[3] is used on 300 slots, andphase changing value P[4] is used on 300 slots.

Furthermore, in order to transmit the first coded block, phase changingvalue P[0] is used on slots 300 times, phase changing value P[1] is usedon slots 300 times, phase changing value P[2] is used on slots 300times, phase changing value P[3] is used on slots 300 times, and phasechanging value P[4] is used on slots 300 times. Furthermore, in order totransmit the second coded block, phase changing value P[0] is used onslots 300 times, phase changing value P[1] is used on slots 300 times,phase changing value P[2] is used on slots 300 times, phase changingvalue P[3] is used on slots 300 times, and phase changing value P[4] isused on slots 300 times.

Furthermore, for the above-described 1000 slots needed to transmit the6000×2 bits making up the two coded blocks when the modulation scheme is64-QAM, phase changing value P[0] is used on 200 slots, phase changingvalue P[1] is used on 200 slots, phase changing value P[2] is used on200 slots, phase changing value P[3] is used on 200 slots, and phasechanging value P[4] is used on 200 slots.

Furthermore, in order to transmit the first coded block, phase changingvalue P[0] is used on slots 200 times, phase changing value P[1] is usedon slots 200 times, phase changing value P[2] is used on slots 200times, phase changing value P[3] is used on slots 200 times, and phasechanging value P[4] is used on slots 200 times. Furthermore, in order totransmit the second coded block, phase changing value P[0] is used onslots 200 times, phase changing value P[1] is used on slots 200 times,phase changing value P[2] is used on slots 200 times, phase changingvalue P[3] is used on slots 200 times, and phase changing value P[4] isused on slots 200 times.

As described above, the phase changing values used in the phase changingmethod regularly switching between phase changing values with a period(cycle) of N are expressed as P[0], P[1] . . . P[N−2], P[N−1]. However,P[0], P[1] . . . P[N−2], P[N−1] should include at least two differentphase changing values (i.e., P[0], P[1] . . . P[N−2], P[N−1] may includeidentical phase changing values). In order to transmit all of the bitsmaking up a single coded block, phase changing value P[0] is used on K₀slots, phase changing value P[1] is used on K₁ slots, phase changingvalue P[i] is used on K_(i) slots (where i=0, 1, 2 . . . N−1 (i being aninteger between 0 and N−1)), and phase changing value P[N−1] is used onK_(N−1) slots, such that Condition #C19 is met.

(Condition #C19)

K₀=K₁ . . . =K_(i)= . . . K_(N−1). That is, K_(a)=K_(b) (∀a and ∀b wherea, b,=0, 1, 2 . . . N−1 (a and b being integers between 0 and N−1),a≠b).In order to transmit all of the bits making up the first coded block,phase changing value P[0] is used K_(0,1) times, phase changing valueP[1] is used K_(1,)1 times, phase changing value P[i] is used K_(i,1)(where i=0, 1, 2 . . . N−1 (i being an integer between 0 and N−1)), andphase changing value P[N−1] is used K_(N−1,1) times.

(Condition #C20)

K_(0,1)=K_(1,1)= . . . K_(i,1)= . . . K_(N−1,1). That is,K_(a,1)=K_(b,1) (∀a and ∀b where a, b,=0, 1, 2 . . . N−1 (a and b beingintegers between 0 and N−1), a≠b).

In order to transmit all of the bits making up the second coded block,phase changing value P[0] is used K_(0,2) times, phase changing valueP[1] is used K_(1,2) times, phase changing value P[i] is used K_(i,2)(where i=0, 1, 2 . . . N−1 (i being an integer between 0 and N−1)), andphase changing value P[N−1] is used K_(N−1,2) times.

(Condition #C21)

K_(0,2)=K_(1,2)= . . . K_(i,2)= . . . K_(N−1,2). That is,K_(a,2)=K_(b,2) (∀a and ∀b where a, b,=0, 1, 2 . . . N−1, a≠b).

Then, when a communication system that supports multiple modulationschemes selects one such supported method for use, Condition #C19,Condition #C20, and Condition #C21 are preferably met for the supportedmodulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #C19, Condition #C20, and Condition #C21 may not be satisfiedfor some modulation schemes. In such a case, the following conditionsapply instead of Condition #C19, Condition #C20, and Condition #C21.

(Condition #C22)

The difference between K_(a) and K_(b) satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (aand b being integers between 0 and N−1), a≠b).

(Condition #C23)

The difference between K_(a,1) and K_(b,1) satisfies 0 or 1. That is,|K_(a,1)−K_(b,1)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1(a and b being integers between 0 and N−1), a≠b).

(Condition #C24)

The difference between K_(a,2) and K_(b,2) satisfies 0 or 1. That is,|K_(a,2)−K_(b,2)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1(a and b being integers between 0 and N−1), a≠b).

As described above, bias among the phase changing values being used totransmit the coded blocks is removed by creating a relationship betweenthe coded block and the phase changing values. As such, data receptionquality can be improved for the reception device.

In the present Embodiment, N phase changing values (or phase changingsets) are needed in order to perform a change of phase having a period(cycle) of N with the method for a regular change of phase. As such, Nphase changing values (or phase changing sets) P[0], P[1], P[2] . . .P[N−2], and P[N−1] are prepared. However, methods exist for ordering thephases in the stated order with respect to the frequency domain. Nolimitation is intended in this regard. The N phase changing values (orphase changing sets) P[0], P[1], P[2] . . . P[N−2], and P[N−1] may alsochange the phases of blocks in the time domain or in the time-frequencydomain to obtain a symbol arrangement as described in Embodiment 1.Although the above examples discuss a phase changing method with aperiod (cycle) of N, the same effects are obtainable using N phasechanging values (or phase changing sets) at random. That is, the N phasechanging values (or phase changing sets) need not always have regularperiodicity. As long as the above-described conditions are satisfied,great quality data reception improvements are realizable for thereception device.

Furthermore, given the existence of modes for spatial multiplexing MIMOmethods, MIMO methods using a fixed precoding matrix, space-time blockcoding methods, single-stream transmission, and methods using a regularchange of phase, the transmission device (broadcaster, base station) mayselect any one of these transmission methods.

As described in Non-Patent Literature 3, spatial multiplexing MIMOmethods involve transmitting signals s1 and s2, which are mapped using aselected modulation scheme, on each of two different antennas. MIMOmethods using a fixed precoding matrix involve performing precoding only(with no change in phase). Further, space-time block coding methods aredescribed in Non-Patent Literature 9, 16, and 17. Single-streamtransmission methods involve transmitting signal s1, mapped with aselected modulation scheme, from an antenna after performingpredetermined processing.

Schemes using multi-carrier transmission such as OFDM involve a firstcarrier group made up of a plurality of carriers and a second carriergroup made up of a plurality of carriers different from the firstcarrier group, and so on, such that multi-carrier transmission isrealized with a plurality of carrier groups. For each carrier group, anyof spatial multiplexing MIMO schemes, MIMO schemes using a fixedprecoding matrix, space-time block coding schemes, single-streamtransmission, and schemes using a regular change of phase may be used.In particular, schemes using a regular change of phase on a selected(sub-)carrier group are preferably used to realize the presentEmbodiment.

When a change of phase by, for example, a phase changing value for P[i]of X radians is performed on only one precoded baseband signal, thephase changers of FIGS. 3, 4, 6, 12, 25, 29, 51, and 53 multiplyprecoded baseband signal z2′ by e^(jX). Then, when a change of phase by,for example, a phase changing set for P[i] of X radians and Y radians isperformed on both precoded baseband signals, the phase changers fromFIGS. 26, 27, 28, 52, and 54 multiply precoded baseband signal z2′ bye^(jX) and multiply precoded baseband signal z1′ by e^(jY).

Embodiment D1

The present Embodiment is first described as a variation ofEmbodiment 1. FIG. 67 illustrates a sample transmission devicepertaining to the present Embodiment. Components thereof operatingidentically to those of FIG. 3 use the same reference numbers thereas,and the description thereof is omitted for simplicity, below. FIG. 67differs from FIG. 3 in the insertion of a baseband signal switcher 6702directly following the weighting units. Accordingly, the followingexplanations are primarily centred on the baseband signal switcher 6702.

FIG. 21 illustrates the configuration of the weighting units 308A and308B. The area of FIG. 21 enclosed in the dashed line represents one ofthe weighting units. Baseband signal 307A is multiplied by w11 to obtainw11·s1(t), and multiplied by w21 to obtain w21·s1(t). Similarly,baseband signal 307B is multiplied by w12 to obtain w12·s2(t), andmultiplied by w22 to obtain w22·s2(t). Next, z1(t)=w11·s1(t)+w12·s2(t)and z2(t)=w21·s1(t)+w22·s22(t) are obtained. Here, as explained inEmbodiment 1, s1(t) and s2(t) are baseband signals modulated accordingto a modulation scheme such as BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM,64-QAM, 256-QAM, 16-APSK and so on. Both weighting units performweighting using a fixed precoding matrix. The precoding matrix uses, forexample, the method of Math. 62 (formula 62), and satisfies theconditions of Math. 63 (formula 63) or Math. 64 (formula 64), all foundbelow. However, this is only an example. The value of a is not limitedto Math. 63 (formula 63) and Math. 64 (formula 64), and may, forexample, be 1, or may be 0 (α is preferably a real number greater thanor equal to 0, but may be also be an imaginary number).

Here, the precoding matrix is

$\begin{matrix}( {{formula}\mspace{14mu} 62} ) & \; \\{\begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix} = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j\; 0} & {\alpha \times ^{j\; 0}} \\{\alpha \times ^{j\; 0}} & ^{j\; \pi}\end{pmatrix}}} & \lbrack {{Math}.\mspace{14mu} 62} \rbrack\end{matrix}$

In Math. 62 (formula 62), above, α is given by:

$\begin{matrix}{\alpha = \frac{\sqrt{2} + 4}{\sqrt{2} + 2}} & \lbrack {{Math}.\mspace{14mu} 63} \rbrack\end{matrix}$

(formula 63)

Alternatively, in Math. 62 (formula 62), above, α may be given by:

$\begin{matrix}{\alpha = \frac{\sqrt{2} + 3 + \sqrt{5}}{\sqrt{2} + 3 - \sqrt{5}}} & \lbrack {{Math}.\mspace{14mu} 64} \rbrack\end{matrix}$

(formula 64)

Alternatively, the precoding matrix is not restricted to that of Math.62 (formula 62), but may also be:

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 65} \rbrack & \; \\{\begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix} = \begin{pmatrix}a & b \\c & d\end{pmatrix}} & ( {{formula}\mspace{14mu} 65} )\end{matrix}$

where a=Ae^(jδ11), b=Be^(jδ12), c=Ce^(jδ21), and d=De^(jδ22). Further,one of a, b, c, and d may be equal to zero. For example: (1) a may bezero while b, c, and d are non-zero, (2) b may be zero while a, c, and dare non-zero, (3) c may be zero while a, b, and d are non-zero, or (4) dmay be zero while a, b, and c are non-zero.

Alternatively, any two of a, b, c, and d may be equal to zero. Forexample, (1) a and d may be zero while b and c are non-zero, or (2) band c may be zero while a and d are non-zero.

When any of the modulation scheme, error-correcting codes, and thecoding rate thereof are changed, the precoding matrix in use may also beset and changed, or the same precoding matrix may be used as-is.

Next, the baseband signal switcher 6702 from FIG. 67 is described. Thebaseband signal switcher 6702 takes weighted signal 309A and weightedsignal 316B as input, performs baseband signal switching, and outputsswitched baseband signal 6701A and switched baseband signal 6701B. Thedetails of baseband signal switching are as described with reference toFIG. 55. The baseband signal switching performed in the presentEmbodiment differs from that of FIG. 55 in terms of the signal used forswitching. The following describes the baseband signal switching of thepresent Embodiment with reference to FIG. 68.

In FIG. 68, weighted signal 309A(p1(i)) has an in-phase component I ofI_(p1)(i) and a quadrature component Q of Q_(p1)(i), while weightedsignal 316B(p2(i)) has an in-phase component I of I_(p2)(i) and aquadrature component Q of Q_(p2)(i). In contrast, switched basebandsignal 6701A(q1(i)) has an in-phase component I of I_(q1)(i) and aquadrature component Q of Q_(q1)(i), while switched baseband signal6701B(q2(i) has an in-phase component I of I_(q2)(i) and a quadraturecomponent Q of Q_(q2)(i). (Here, i represents (time or (carrier)frequency order. In the example of FIG. 67, i represents time, though imay also represent (carrier) frequency when FIG. 67 is applied to anOFDM scheme, as in FIG. 12. These points are elaborated upon below.)

Here, the baseband components are switched by the baseband signalswitcher 6702, such that:

-   -   For switched baseband signal q1(i), the in-phase component I may        be I_(p1)(i) while the quadrature component Q may be Q_(p2)(i),        and for switched baseband signal q2(i), the in-phase component I        may be I_(p2)(i) while the quadrature component q may be        Q_(p1)(i). The modulated signal corresponding to switched        baseband signal q1(i) is transmitted by transmit antenna 1 and        the modulated signal corresponding to switched baseband signal        q2(i) is transmitted from transmit antenna 2, simultaneously on        a common frequency. As such, the modulated signal corresponding        to switched baseband signal q1(i) and the modulated signal        corresponding to switched baseband signal q2(i) are transmitted        from different antennas, simultaneously on a common frequency.        Alternatively,    -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be I_(p2)(i),        and for switched baseband signal q2(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        Q_(p2)(i).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q2(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        Q_(p2)(i).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be I_(p2)(i),        and for switched baseband signal q2(i), the in-phase component        may be Q_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q2(i), the in-phase component        may be Q_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be Q_(p2)(i),        and for switched baseband signal q2(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        I_(p2)(i).    -   For switched baseband signal q1(i), the in-phase component may        be Q_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q2(i), the in-phase component        may be I_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q1(i), the in-phase component may        be Q_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q2(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        I_(p2)(i).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be I_(p2)(i),        and for switched baseband signal q1(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        Q_(p2)(i).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q1(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        Q_(p2)(i).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be I_(p2)(i),        and for switched baseband signal q1(i), the in-phase component        may be Q_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q1(i), the in-phase component        may be Q_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be Q_(p2)(i),        and for switched baseband signal q1(i), the in-phase component        may be I_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i) while the quadrature component may be Q_(p2)(i),        and for switched baseband signal q1(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        I_(p2)(i).    -   For switched baseband signal q2(i), the in-phase component may        be Q_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q1(i), the in-phase component        may be I_(p2)(i) while the quadrature component may be        Q_(p1)(i).    -   For switched baseband signal q2(i), the in-phase component may        be Q_(p2)(i) while the quadrature component may be I_(p1)(i),        and for switched baseband signal q1(i), the in-phase component        may be Q_(p1)(i) while the quadrature component may be        I_(p2)(i).

Alternatively, the weighted signals 309A and 316B are not limited to theabove-described switching of in-phase component and quadraturecomponent. Switching may be performed on in-phase components andquadrature components greater than those of the two signals.

Also, while the above examples describe switching performed on basebandsignals having a common timestamp (common (sub-)carrier) frequency), thebaseband signals being switched need not necessarily have a commontimestamp (common (sub-)carrier) frequency). For example, any of thefollowing are possible.

-   -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        Q_(p2)(i+w), and for switched baseband signal q2(i), the        in-phase component may be I_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        I_(p2)(i+w), and for switched baseband signal q2(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be Q_(p2)(i+w).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q2(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be Q_(p2)(i+w).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        I_(p2)(i+w), and for switched baseband signal q2(i), the        in-phase component may be Q_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q2(i), the        in-phase component may be Q_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q1(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        Q_(p2)(i+w), and for switched baseband signal q2(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be I_(p2)(i+w).    -   For switched baseband signal q1(i), the in-phase component may        be Q_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q2(i), the        in-phase component may be I_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q1(i), the in-phase component may        be Q_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q2(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be I_(p2)(i+w).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        I_(p2)(i+w), and for switched baseband signal q1(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be Q_(p2)(i+w).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q1(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be Q_(p2)(i+w).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        I_(p2)(i+w), and for switched baseband signal q1(i), the        in-phase component may be Q_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q1(i), the        in-phase component may be Q_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        Q_(p2)(i+w), and for switched baseband signal q1(i), the        in-phase component may be I_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q2(i), the in-phase component may        be I_(p1)(i+v) while the quadrature component may be        Q_(p2)(i+w), and for switched baseband signal q1(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be I_(p2)(i+w).    -   For switched baseband signal q2(i), the in-phase component may        be Q_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q1(i), the        in-phase component may be I_(p2)(i+w) while the quadrature        component may be Q_(p1)(i+v).    -   For switched baseband signal q2(i), the in-phase component may        be Q_(p2)(i+w) while the quadrature component may be        I_(p1)(i+v), and for switched baseband signal q1(i), the        in-phase component may be Q_(p1)(i+v) while the quadrature        component may be I_(p2)(i+w).

Here, weighted signal 309A(p1(i)) has an in-phase component I ofI_(p1)(i) and a quadrature component Q of Q_(p1)(i), while weightedsignal 316B(p2(i)) has an in-phase component I of I_(p2)(i) and aquadrature component Q of Q_(p2)(i). In contrast, switched basebandsignal 6701A(q1(i)) has an in-phase component I of I_(q1)(i) and aquadrature component Q of Q_(q1)(i), while switched baseband signal6701B(q2(i)) has an in-phase component I_(q2)(i) and a quadraturecomponent Q of Q_(q2)(i).

In FIG. 68, as described above, weighted signal 309A(p1(i)) has anin-phase component I of I_(p1)(i) and a quadrature component Q ofQ_(p1)(i), while weighted signal 316B(p2(i)) has an in-phase component Iof I_(p2)(i) and a quadrature component Q of Q_(p2)(i). In contrast,switched baseband signal 6701A(q1(i)) has an in-phase component I ofI_(q1)(i) and a quadrature component Q of Q_(q1)(i), while switchedbaseband signal 6701B(q2(i)) has an in-phase component I_(q2)(i) and aquadrature component Q of Q_(q2)(i).

As such, in-phase component I of I_(q1)(i) and quadrature component Q ofQ_(q1)(i) of switched baseband signal 6701A(q1(i)) and in-phasecomponent I_(q2)(i) and quadrature component Q of Q_(q2)(i) of basebandsignal 6701B(q2(i)) are expressible as any of the above.

As such, the modulated signal corresponding to switched baseband signal6701A(q1(i)) is transmitted from transmit antenna 312A, while themodulated signal corresponding to switched baseband signal 6701B(q2(i))is transmitted from transmit antenna 312B, both being transmittedsimultaneously on a common frequency. Thus, the modulated signalscorresponding to switched baseband signal 6701A(q1(i)) and switchedbaseband signal 6701B(q2(i)) are transmitted from different antennas,simultaneously on a common frequency.

Phase changer 317B takes switched baseband signal 6701B and signalprocessing method information 315 as input and regularly changes thephase of switched baseband signal 6701B for output. This regular changeis a change of phase performed according to a predetermined phasechanging pattern having a predetermined period (cycle) (e.g., every nsymbols (n being an integer, n≧1) or at a predetermined interval). Thephase changing pattern is described in detail in Embodiment 4.

Wireless unit 310B takes post-phase change signal 309B as input andperforms processing such as quadrature modulation, band limitation,frequency conversion, amplification, and so on, then outputs transmitsignal 311B. Transmit signal 311B is then output as radio waves by anantenna 312B.

FIG. 67, much like FIG. 3, is described as having a plurality ofencoders. However, FIG. 67 may also have an encoder and a distributorlike FIG. 4. In such a case, the signals output by the distributor arethe respective input signals for the interleaver, while subsequentprocessing remains as described above for FIG. 67, despite the changesrequired thereby.

FIG. 5 illustrates an example of a frame configuration in the timedomain for a transmission device according to the present Embodiment.Symbol 500_1 is a symbol for notifying the reception device of thetransmission method. For example, symbol 500_1 conveys information suchas the error-correction method used for transmitting data symbols, thecoding rate thereof, and the modulation scheme used for transmittingdata symbols.

Symbol 501_1 is for estimating channel fluctuations for modulated signalz1(t) (where t is time) transmitted by the transmission device. Symbol502_1 is a data symbol transmitted by modulated signal z1(t) as symbolnumber u (in the time domain). Symbol 503_1 is a data symbol transmittedby modulated signal z1(t) as symbol number u+1.

Symbol 501_2 is for estimating channel fluctuations for modulated signalz2(t) (where t is time) transmitted by the transmission device. Symbol502_2 is a data symbol transmitted by modulated signal z2(t) as symbolnumber u. Symbol 503_2 is a data symbol transmitted by modulated signalz1(t) as symbol number u+1.

Here, the symbols of z1(t) and of z2(t) having the same timestamp(identical timing) are transmitted from the transmit antenna using thesame (shared/common) frequency.

The following describes the relationships between the modulated signalsz1 (t) and z2(t) transmitted by the transmission device and the receivedsignals r1(t) and r2(t) received by the reception device.

In FIG. 5, 504#1 and 504#2 indicate transmit antennas of thetransmission device, while 505#1 and 505#2 indicate receive antennas ofthe reception device. The transmission device transmits modulated signalz1(t) from transmit antenna 504#1 and transmits modulated signal z2(t)from transmit antenna 504#2. Here, modulated signals z1(t) and z2(t) areassumed to occupy the same (shared/common) frequency (bandwidth). Thechannel fluctuations in the transmit antennas of the transmission deviceand the antennas of the reception device are h₁₁(t), h₁₂(t), h₂₁(t), andh₂₂(t), respectively. Assuming that receive antenna 505#1 of thereception device receives received signal r1(t) and that receive antenna505#2 of the reception device receives received signal r2(t), thefollowing relationship holds.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 66} \rbrack & \; \\{\begin{pmatrix}{r\; 1(t)} \\{r\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h_{11}(t)} & {h_{12}(t)} \\{h_{21}(t)} & {h_{22}(t)}\end{pmatrix}\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix}}} & ( {{formula}\mspace{14mu} 66} )\end{matrix}$

FIG. 69 pertains to the weighting method (precoding method), thebaseband switching method, and the phase changing method of the presentEmbodiment. The weighting unit 600 is a combined version of theweighting units 308A and 308B from FIG. 67. As shown, stream s1(t) andstream s2(t) correspond to the baseband signals 307A and 307B of FIG. 3.That is, the streams s1(t) and s2(t) are baseband signals made up of anin-phase component I and a quadrature component Q conforming to mappingby a modulation scheme such as QPSK, 16-QAM, and 64-QAM. As indicated bythe frame configuration of FIG. 69, stream s1(t) is represented as s1(u)at symbol number u, as s1(u+1) at symbol number u+1, and so forth.Similarly, stream s2(t) is represented as s2(u) at symbol number u, ass2(u+1) at symbol number u+1, and so forth. The weighting unit 600 takesthe baseband signals 307A (s1(t)) and 307B (s2(t)) as well as the signalprocessing method information 315 from FIG. 67 as input, performsweighting in accordance with the signal processing method information315, and outputs the weighted signals 309A (_(p1)(t)) and 316B(_(p2)(t))from FIG. 67.

Here, given vector W1=(w11,w12) from the first row of the fixedprecoding matrix F, p₁(t) can be expressed as Math. 67 (formula 67),below.

[Math. 67]

p1(t)=W1s1(t)  (formula 67)

Here, given vector W2=(w21,w22) from the first row of the fixedprecoding matrix F, p₂(t) can be expressed as Math. 68 (formula 68),below.

[Math. 68]

p2(t)=W2s2(t)  (formula 68)

Accordingly, precoding matrix F may be expressed as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 69} \rbrack & \; \\{F = \begin{pmatrix}{w\; 11} & {w\; 12} \\{w\; 21} & {w\; 22}\end{pmatrix}} & ( {{formula}\mspace{14mu} 69} )\end{matrix}$

After the baseband signals have been switched, switched baseband signal6701A(q₁(i)) has an in-phase component I of Iq₁(i) and a quadraturecomponent Q of Qp₁(i), and switched baseband signal 6701B(q₂(i)) has anin-phase component I of Iq₂(i) and a quadrature component Q of Qq₂(i).The relationships between all of these are as stated above. When thephase changer uses phase changing formula y(t), the post-phase changebaseband signal 309B(q′2(i)) is given by Math. 70 (formula 70), below.

[Math. 70]

q2′(t)=y(t)q2(t)  (formula 70)

Here, y(t) is a phase changing formula obeying a predetermined method.For example, given a period (cycle) of four and timestamp u, the phasechanging formula may be expressed as Math. 71 (formula 71), below.

[Math. 71]

y(u)=e ¹⁰  (formula 71)

Similarly, the phase changing formula for timestamp u+1 may be, forexample, as given by Math. 72 (formula 72).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 72} \rbrack & \; \\{{y( {u + 1} )} = ^{j\frac{\pi}{2}}} & ( {{formula}\mspace{14mu} 72} )\end{matrix}$

That is, the phase changing formula for timestamp u+k generalizes toMath. 73 (formula 73).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 73} \rbrack & \; \\{{y( {u + k} )} = ^{j\frac{k\; \pi}{2}}} & ( {{formula}\mspace{14mu} 73} )\end{matrix}$

Note that Math. 71 (formula 71) through Math. 73 (formula 73) are givenonly as an example of a regular change of phase.

The regular change of phase is not restricted to a period (cycle) offour. Improved reception capabilities (the error-correctioncapabilities, to be exact) may potentially be promoted in the receptiondevice by increasing the period (cycle) number (this does not mean thata greater period (cycle) is better, though avoiding small numbers suchas two is likely ideal).

Furthermore, although Math. 71 (formula 71) through Math. 73 (formula73), above, represent a configuration in which a change of phase iscarried out through rotation by consecutive predetermined phases (in theabove formula, every π/2), the change of phase need not be rotation by aconstant amount but may also be random. For example, in accordance withthe predetermined period (cycle) of y(t), the phase may be changedthrough sequential multiplication as shown in Math. 74 (formula 74) andMath. 75 (formula 75). The key point of the regular change of phase isthat the phase of the modulated signal is regularly changed. The phasechanging degree variance rate is preferably as even as possible, such asfrom −π radians to π radians. However, given that this concerns adistribution, random variance is also possible.

$\begin{matrix}{\mspace{79mu} \lbrack {{Math}.\mspace{14mu} 74} \rbrack} & \; \\ ^{j\; 0}arrow ^{j\frac{\pi}{5}}arrow ^{j\frac{2\; \pi}{5}}arrow ^{j\frac{3\; \pi}{5}}arrow ^{j\frac{4\; \pi}{5}}arrow ^{j\pi}arrow ^{j\frac{6\; \pi}{5}}arrow ^{j\frac{7\; \pi}{5}}arrow ^{j\frac{8\; \pi}{5}}arrow ^{j\frac{9\; \pi}{5}}          & ( {{formula}\mspace{14mu} 74} ) \\{\mspace{76mu} \lbrack {{Math}.\mspace{14mu} 75} \rbrack} & \; \\ ^{j\; \frac{\pi}{2}}arrow ^{j\pi}arrow ^{j\frac{3\; \pi}{2}}arrow ^{{j2}\; \pi}arrow ^{j\frac{\pi}{4}}arrow ^{j\frac{3}{4}\pi}arrow ^{j\frac{5\; \pi}{4}}arrow ^{j\frac{7\; \pi}{4}}        & ( {{formula}\mspace{14mu} 75} )\end{matrix}$

As such, the weighting unit 600 of FIG. 6 performs precoding usingfixed, predetermined precoding weights, the baseband signal switcherperforms baseband signal switching as described above, and the phasechanger changes the phase of the signal input thereto while regularlyvarying the degree of change.

When a specialized precoding matrix is used in the LOS environment, thereception quality is likely to improve tremendously. However, dependingon the direct wave conditions, the phase and amplitude components of thedirect wave may greatly differ from the specialized precoding matrix,upon reception. The LOS environment has certain rules. Thus, datareception quality is tremendously improved through a regular change oftransmit signal phase that obeys those rules. The present inventionoffers a signal processing method for improving the LOS environment.

FIG. 7 illustrates a sample configuration of a reception device 700pertaining to the present embodiment. Wireless unit 703_X receives, asinput, received signal 702_X received by antenna 701_X, performsprocessing such as frequency conversion, quadrature demodulation, andthe like, and outputs baseband signal 704_X.

Channel fluctuation estimator 705_1 for modulated signal z1 transmittedby the transmission device takes baseband signal 704_X as input,extracts reference symbol 501_1 for channel estimation from FIG. 5,estimates the value of h₁₁ from Math. 66 (formula 66), and outputschannel estimation signal 706_1.

Channel fluctuation estimator 705_2 for modulated signal z2 transmittedby the transmission device takes baseband signal 704_X as input,extracts reference symbol 501_2 for channel estimation from FIG. 5,estimates the value of h₁₂ from Math. 66 (formula 66), and outputschannel estimation signal 706_2.

Wireless unit 703_Y receives, as input, received signal 702_Y receivedby antenna 701_X, performs processing such as frequency conversion,quadrature demodulation, and the like, and outputs baseband signal704_Y.

Channel fluctuation estimator 707_1 for modulated signal z1 transmittedby the transmission device takes baseband signal 704_Y as input,extracts reference symbol 501_1 for channel estimation from FIG. 5,estimates the value of h₂₁ from Math. 66 (formula 66), and outputschannel estimation signal 708_1.

Channel fluctuation estimator 707_2 for modulated signal z2 transmittedby the transmission device takes baseband signal 704_Y as input,extracts reference symbol 501_2 for channel estimation from FIG. 5,estimates the value of h₂₂ from Math. 66 (formula 66), and outputschannel estimation signal 708_2.

A control information decoder 709 receives baseband signal 704_X andbaseband signal 704_Y as input, detects symbol 500_1 that indicates thetransmission method from FIG. 5, and outputs a transmission devicetransmission method information signal 710.

A signal processor 711 takes the baseband signals 704_X and 704_Y, thechannel estimation signals 706_1, 706_2, 708_1, and 708_2, and thetransmission method information signal 710 as input, performs detectionand decoding, and then outputs received data 712_1 and 712_2.

Next, the operations of the signal processor 711 from FIG. 7 aredescribed in detail. FIG. 8 illustrates a sample configuration of thesignal processor 711 pertaining to the present embodiment. As shown, thesignal processor 711 is primarily made up of an inner MIMO detector, asoft-in/soft-out decoder, and a coefficient generator. Non-PatentLiterature 2 and Non-Patent Literature 3 describe the method ofiterative decoding with this structure. The MIMO system described inNon-Patent Literature 2 and Non-Patent Literature 3 is a spatialmultiplexing MIMO system, while the present Embodiment differs fromNon-Patent Literature 2 and Non-Patent Literature 3 in describing a MIMOsystem that regularly changes the phase over time, while using theprecoding matrix and performing baseband signal switching. Taking the(channel) matrix H(t) of Math. 66 (formula 66), then by letting theprecoding weight matrix from FIG. 69 be F (here, a fixed precodingmatrix remaining unchanged for a given received signal) and letting thephase changing formula used by the phase changer from FIG. 69 be Y(t)(here, Y(t) changes over time t), then given the baseband signalswitching, the receive vector R(t)=(r1(t),r2(t))^(T) and the streamvector S(t)=(s1(t),s2(t))^(T) lead to the decoding method of Non-PatentLiterature 2 and Non-Patent Literature 3, thus enabling MIMO detection.

Accordingly, the coefficient generator 819 from FIG. 8 takes atransmission method information signal 818 (corresponding to 710 fromFIG. 7) indicated by the transmission device (information for specifyingthe fixed precoding matrix in use and the phase changing pattern usedwhen the phase is changed) and outputs a signal processing methodinformation signal 820.

The inner MIMO detector 803 takes the signal processing methodinformation signal 820 as input and performs iterative detection anddecoding using the signal. The operations are described below.

The processing unit illustrated in FIG. 8 must use a processing method,as is illustrated in FIG. 10, to perform iterative decoding (iterativedetection). First, detection of one codeword (or one frame) of modulatedsignal (stream) s1 and of one codeword (or one frame) of modulatedsignal (stream) s2 are performed. As a result, the soft-in/soft-outdecoder obtains the log-likelihood ratio of each bit of the codeword (orframe) of modulated signal (stream) s1 and of the codeword (or frame) ofmodulated signal (stream) s2. Next, the log-likelihood ratio is used toperform a second round of detection and decoding. These operations(referred to as iterative decoding (iterative detection)) are performedmultiple times. The following explanations centre on the creation methodof the log-likelihood ratio of a symbol at a specific time within oneframe.

In FIG. 8, a memory 815 takes baseband signal 801X (corresponding tobaseband signal 704_X from FIG. 7), channel estimation signal group 802X(corresponding to channel estimation signals 706_1 and 706_2 from FIG.7), baseband signal 801Y (corresponding to baseband signal 704_Y fromFIG. 7), and channel estimation signal group 802Y (corresponding tochannel estimation signals 708_1 and 708_2 from FIG. 7) as input,performs iterative decoding (iterative detection), and stores theresulting matrix as a transformed channel signal group. The memory 815then outputs the above-described signals as needed, specifically asbaseband signal 816X, transformed channel estimation signal group 817X,baseband signal 816Y, and transformed channel estimation signal group817Y.

Subsequent operations are described separately for initial detection andfor iterative decoding (iterative detection).

(Initial Detection)

The inner MIMO detector 803 takes baseband signal 801X, channelestimation signal group 802X, baseband signal 801Y, and channelestimation signal group 802Y as input. Here, the modulation scheme formodulated signal (stream) s1 and modulated signal (stream) s2 isdescribed as 16-QAM.

The inner MIMO detector 803 first computes a candidate signal pointcorresponding to baseband signal 801X from the channel estimation signalgroups 802X and 802Y. FIG. 11 represents such a calculation. In FIG. 11,each black dot is a candidate signal point in the I-Q plane. Given thatthe modulation scheme is 16-QAM, 256 candidate signal points exist.(However, FIG. 11 is only a representation and does not indicate all 256candidate signal points.) Letting the four bits transmitted in modulatedsignal s1 be b0, b1, b2, and b3 and the four bits transmitted inmodulated signal s2 be b4, b5, b6, and b7, candidate signal pointscorresponding to (b0, b1, b2, b3, b4, b5, b6, b7) are found in FIG. 11.The Euclidean squared distance between each candidate signal point andeach received signal point 1101 (corresponding to baseband signal 801X)is then computed. The Euclidian squared distance between each point isdivided by the noise variance σ². Accordingly, E_(X)(b0, b1, b2, b3, b4,b5, b6, b7) is calculated. That is, the Euclidian squared distancebetween a candidate signal point corresponding to (b0, b1, b2, b3, b4,b5, b6, b7) and a received signal point is divided by the noisevariance. Here, each of the baseband signals and the modulated signalss1 and s2 is a complex signal.

Similarly, the inner MIMO detector 803 calculates candidate signalpoints corresponding to baseband signal 801Y from channel estimationsignal group 802X and channel estimation signal group 802Y, computes theEuclidean squared distance between each of the candidate signal pointsand the received signal points (corresponding to baseband signal 801Y),and divides the Euclidean squared distance by the noise variance σ2.Accordingly, E_(Y)(b0, b1, b2, b3, b4, b5, b6, b7) is calculated. Thatis, E_(Y) is the Euclidian squared distance between a candidate signalpoint corresponding to (b0, b1, b2, b3, b4, b5, b6, b7) and a receivedsignal point, divided by the noise variance.

Next, E_(X)(b0, b1, b2, b3, b4, b5, b6, b7)+E_(Y)(b0, b1, b2, b3, b4,b5, b6, b7)=E(b0, b1, b2, b3, b4, b5, b6, b7) is computed.

The inner MIMO detector 803 outputs E(b0, b1, b2, b3, b4, b5, b6, b7) asthe signal 804.

Log-likelihood calculator 805A takes the signal 804 as input, calculatesthe log-likelihood of bits b0, b1, b2, and b3, and outputs alog-likelihood signal 806A. Note that this log-likelihood calculationproduces the log-likelihood of a bit being 1 and the log-likelihood of abit being 0. The calculation method is as shown in Math. 28 (formula28), Math. 29 (formula 29), and Math. 30 (formula 30), and the detailsare given by Non-Patent Literature 2 and 3.

Similarly, log-likelihood calculator 805B takes the signal 804 as input,calculates the log-likelihood of bits b4, b5, b6, and b7, and outputslog-likelihood signal 806B.

A deinterleaver (807A) takes log-likelihood signal 806A as input,performs deinterleaving corresponding to that of the interleaver (theinterleaver (304A) from FIG. 67), and outputs deinterleavedlog-likelihood signal 808A.

Similarly, a deinterleaver (807B) takes log-likelihood signal 806B asinput, performs deinterleaving corresponding to that of the interleaver(the interleaver (6704B) from FIG. 67), and outputs deinterleavedlog-likelihood signal 808B.

Log-likelihood ratio calculator 809A takes deinterleaved log-likelihoodsignal 808A as input, calculates the log-likelihood ratio of the bitsencoded by encoder 6702A from FIG. 67, and outputs log-likelihood ratiosignal 810A.

Similarly, log-likelihood ratio calculator 809B takes deinterleavedlog-likelihood signal 808B as input, calculates the log-likelihood ratioof the bits encoded by encoder 302B from FIG. 67, and outputslog-likelihood ratio signal 810B.

Soft-in/soft-out decoder 811A takes log-likelihood ratio signal 810A asinput, performs decoding, and outputs a decoded log-likelihood ratio812A.

Similarly, soft-in/soft-out decoder 811B takes log-likelihood ratiosignal 810B as input, performs decoding, and outputs decodedlog-likelihood ratio 812B.

(Iterative Decoding (Iterative Detection), k Iterations)

The interleaver (813A) takes the k−1th decoded log-likelihood ratio 812Adecoded by the soft-in/soft-out decoder as input, performs interleaving,and outputs interleaved log-likelihood ratio 814A. Here, theinterleaving pattern used by the interleaver (813A) is identical to thatof the interleaver (304A) from FIG. 67.

Another interleaver (813B) takes the k−1th decoded log-likelihood ratio812B decoded by the soft-in/soft-out decoder as input, performsinterleaving, and outputs interleaved log-likelihood ratio 814B. Here,the interleaving pattern used by the interleaver (813B) is identical tothat of the other interleaver (304B) from FIG. 67.

The inner MIMO detector 803 takes baseband signal 816X, transformedchannel estimation signal group 817X, baseband signal 816Y, transformedchannel estimation signal group 817Y, interleaved log-likelihood ratio814A, and interleaved log-likelihood ratio 814B as input. Here, basebandsignal 816X, transformed channel estimation signal group 817X, basebandsignal 816Y, and transformed channel estimation signal group 817Y areused instead of baseband signal 801X, channel estimation signal group802X, baseband signal 801Y, and channel estimation signal group 802Ybecause the latter cause delays due to the iterative decoding.

The iterative decoding operations of the inner MIMO detector 803 differfrom the initial detection operations thereof in that the interleavedlog-likelihood ratios 814A and 814B are used in signal processing forthe former. The inner MIMO detector 803 first calculates E(b0, b1, b2,b3, b4, b5, b6, b7) in the same manner as for initial detection. Inaddition, the coefficients corresponding to Math. 11 (formula 11) andMath. 32 (formula 32) are computed from the interleaved log-likelihoodratios 814A and 914B. The value of E(b0, b1, b2, b3, b4, b5, b6, b7) iscorrected using the coefficients so calculated to obtain E′(b0, b1, b2,b3, b4, b5, b6, b7), which is output as the signal 804.

The log-likelihood calculator 805A takes the signal 804 as input,calculates the log-likelihood of bits b0, b1, b2, and b3, and outputsthe log-likelihood signal 806A. Note that this log-likelihoodcalculation produces the log-likelihood of a bit being 1 and thelog-likelihood of a bit being 0. The calculation method is as shown inMath. 31 (formula 31) through Math. 35 (formula 35), and the details aregiven by Non-Patent Literature 2 and 3.

Similarly, log-likelihood calculator 805B takes the signal 804 as input,calculates the log-likelihood of bits b4, b5, b6, and b7, and outputslog-likelihood signal 806B. Operations performed by the deinterleaveronwards are similar to those performed for initial detection.

While FIG. 8 illustrates the configuration of the signal processor whenperforming iterative detection, this structure is not absolutelynecessary as good reception improvements are obtainable by iterativedetection alone. As long as the components needed for iterativedetection are present, the configuration need not include theinterleavers 813A and 813B. In such a case, the inner MIMO detector 803does not perform iterative detection.

As shown in Non-Patent Literature 5 and the like, QR decomposition mayalso be used to perform initial detection and iterative detection. Also,as indicated by Non-Patent Literature 11, MMSE and ZF linear operationsmay be performed when performing initial detection.

FIG. 9 illustrates the configuration of a signal processor unlike thatof FIG. 8, that serves as the signal processor for modulated signalstransmitted by the transmission device from FIG. 4 as used in FIG. 67.The point of difference from FIG. 8 is the number of soft-in/soft-outdecoders. A soft-in/soft-out decoder 901 takes the log-likelihood ratiosignals 810A and 810B as input, performs decoding, and outputs a decodedlog-likelihood ratio 902. A distributor 903 takes the decodedlog-likelihood ratio 902 as input for distribution. Otherwise, theoperations are identical to those explained for FIG. 8.

As described above, when a transmission device according to the presentEmbodiment using a MIMO system transmits a plurality of modulatedsignals from a plurality of antennas, changing the phase over time whilemultiplying by the precoding matrix so as to regularly change the phaseresults in improvements to data reception quality for a reception devicein a LOS environment, where direct waves are dominant, compared to aconventional spatial multiplexing MIMO system.

In the present Embodiment, and particularly in the configuration of thereception device, the number of antennas is limited and explanations aregiven accordingly. However, the Embodiment may also be applied to agreater number of antennas. In other words, the number of antennas inthe reception device does not affect the operations or advantageouseffects of the present Embodiment.

Further, in the present Embodiments, the encoding is not particularlylimited to LDPC codes. Similarly, the decoding method is not limited toimplementation by a soft-in/soft-out decoder using sum-product decoding.The decoding method used by the soft-in/soft-out decoder may also be,for example, the BCJR algorithm, SOYA, and the Max-Log-Map algorithm.Details are provided in Non-Patent Literature 6.

In addition, although the present Embodiment is described using asingle-carrier method, no limitation is intended in this regard. Thepresent Embodiment is also applicable to multi-carrier transmission.Accordingly, the present Embodiment may also be realized using, forexample, spread-spectrum communications, OFDM, SC-FDMA, SC-OFDM, waveletOFDM as described in Non-Patent Literature 7, and so on. Furthermore, inthe present Embodiment, symbols other than data symbols, such as pilotsymbols (preamble, unique word, and so on) or symbols transmittingcontrol information, may be arranged within the frame in any manner

The following describes an example in which OFDM is used as amulti-carrier method.

FIG. 70 illustrates the configuration of a transmission device usingOFDM. In FIG. 70, components operating in the manner described for FIGS.3, 12, and 67 use identical reference numbers.

An OFDM-related processor 1201A takes weighted signal 309A as input,performs OFDM-related processing thereon, and outputs transmit signal1202A. Similarly, OFDM-related processor 1201B takes post-phase changesignal 309B as input, performs OFDM-related processing thereon, andoutputs transmit signal 1202B.

FIG. 13 illustrates a sample configuration of the OFDM-relatedprocessors 1201A and 1201B and onward from FIG. 70. Components 1301Athrough 1310A belong between 1201A and 312A from FIG. 70, whilecomponents 1301B through 1310B belong between 1201B and 312B.

Serial-to-parallel converter 1302A performs serial-to-parallelconversion on switched baseband signal 1301A (corresponding to switchedbaseband signal 6701A from FIG. 70) and outputs parallel signal 1303A.

Reorderer 1304A takes parallel signal 1303A as input, performsreordering thereof, and outputs reordered signal 1305A. Reordering isdescribed in detail later.

IFFT unit 1306A takes reordered signal 1305A as input, applies an IFFTthereto, and outputs post-IFFT signal 1307A.

Wireless unit 1308A takes post-IFFT signal 1307A as input, performsprocessing such as frequency conversion and amplification, thereon, andoutputs modulated signal 1309A. Modulated signal 1309A is then output asradio waves by antenna 1310A.

Serial-to-parallel converter 1302B performs serial-to-parallelconversion on post-phase change 1301B (corresponding to post-phasechange 309B from FIG. 12) and outputs parallel signal 1303B.

Reorderer 1304B takes parallel signal 1303B as input, performsreordering thereof, and outputs reordered signal 1305B. Reordering isdescribed in detail later.

IFFT unit 1306B takes reordered signal 1305B as input, applies an IFFTthereto, and outputs post-IFFT signal 1307B.

Wireless unit 1308B takes post-IFFT signal 1307B as input, performsprocessing such as frequency conversion and amplification thereon, andoutputs modulated signal 1309B. Modulated signal 1309B is then output asradio waves by antenna 1310A.

The transmission device from FIG. 67 does not use a multi-carriertransmission method. Thus, as shown in FIG. 69, a change of phase isperformed to achieve a period (cycle) of four and the post-phase changesymbols are arranged in the time domain. As shown in FIG. 70, whenmulti-carrier transmission, such as OFDM, is used, then, naturally,symbols in precoded baseband signals having undergone switching andphase changing may be arranged in the time domain as in FIG. 67, andthis may be applied to each (sub-)carrier. However, for multi-carriertransmission, the arrangement may also be in the frequency domain, or inboth the frequency domain and the time domain. The following describesthese arrangements.

FIGS. 14A and 14B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13.The frequency axes are made up of (sub-)carriers 0 through 9. Themodulated signals z1 and z2 share common timestamps (timing) and use acommon frequency band. FIG. 14A illustrates a reordering method for thesymbols of modulated signal z1, while FIG. 14B illustrates a reorderingmethod for the symbols of modulated signal z2. With respect to thesymbols of switched baseband signal 1301A input to serial-to-parallelconverter 1302A, the ordering is #0, #1, #2, #3, and so on. Here, giventhat the example deals with a period (cycle) of four, #0, #1, #2, and #3are equivalent to one period (cycle). Similarly, #4n, #4n+1, #4n+2, and#4n+3 (n being a non-zero positive integer) are also equivalent to oneperiod (cycle).

As shown in FIG. 14A, symbols #0, #1, #2, #3, and so on are arranged inorder, beginning at carrier 0. Symbols #0 through #9 are given timestamp$1, followed by symbols #10 through #19 which are given timestamp #2,and so on in a regular arrangement. Here, modulated signals z1 and z2are complex signals.

Similarly, with respect to the symbols of weighted signal 1301B input toserial-to-parallel converter 1302B, the assigned ordering is #0, #1, #2,#3, and so on. Here, given that the example deals with a period (cycle)of four, a different change in phase is applied to each of #0, #1, #2,and #3, which are equivalent to one period (cycle). Similarly, adifferent change in phase is applied to each of #4n, #4n+1, #4n+2, and#4n+3 (n being a non-zero positive integer), which are also equivalentto one period (cycle).

As shown in FIG. 14B, symbols #0, #1, #2, #3, and so on are arranged inorder, beginning at carrier 0. Symbols #0 through #9 are given timestamp$1, followed by symbols #10 through #19 which are given timestamp $2,and so on in a regular arrangement.

The symbol group 1402 shown in FIG. 14B corresponds to one period(cycle) of symbols when the phase changing method of FIG. 69 is used.Symbol #0 is the symbol obtained by using the phase at timestamp u inFIG. 69, symbol #1 is the symbol obtained by using the phase attimestamp u+1 in FIG. 69, symbol #2 is the symbol obtained by using thephase at timestamp u+2 in FIG. 69, and symbol #3 is the symbol obtainedby using the phase at timestamp u+3 in FIG. 69. Accordingly, for anysymbol #x, symbol #x is the symbol obtained by using the phase attimestamp u in FIG. 69 when x mod 4 equals 0 (i.e., when the remainderof x divided by 4 is 0, mod being the modulo operator), symbol #x is thesymbol obtained by using the phase at timestamp x+1 in FIG. 69 when xmod 4 equals 1, symbol #x is the symbol obtained by using the phase attimestamp x+2 in FIG. 69 when x mod 4 equals 2, and symbol #x is thesymbol obtained by using the phase at timestamp x+3 in FIG. 69 when xmod 4 equals 3.

In the present Embodiment, modulated signal z1 shown in FIG. 14A has notundergone a change of phase.

As such, when using a multi-carrier transmission method such as OFDM,and unlike single carrier transmission, symbols can be arranged in thefrequency domain. Of course, the symbol arrangement method is notlimited to those illustrated by FIGS. 14A and 14B. Further examples areshown in FIGS. 15A, 15B, 16A, and 16B.

FIGS. 15A and 15B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering scheme used by the reorderers 1301A and 1301B from FIG. 13that differs from that of FIGS. 14A and 14B. FIG. 15A illustrates areordering scheme for the symbols of modulated signal z1, while FIG. 15Billustrates a reordering scheme for the symbols of modulated signal z2.FIGS. 15A and 15B differ from FIGS. 14A and 14B in that differentreordering methods are applied to the symbols of modulated signal z1 andto the symbols of modulated signal z2. In FIG. 15B, symbols #0 through#5 are arranged at carriers 4 through 9, symbols #6 though #9 arearranged at carriers 0 through 3, and this arrangement is repeated forsymbols #10 through #19. Here, as in FIG. 14B, symbol group 1502 shownin FIG. 15B corresponds to one period (cycle) of symbols when the phasechanging method of FIG. 6 is used.

FIGS. 16A and 16B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from that of FIGS. 14A and 14B. FIG. 16A illustrates areordering method for the symbols of modulated signal z1, while FIG. 16Billustrates a reordering method for the symbols of modulated signal z2.FIGS. 16A and 16B differ from FIGS. 14A and 14B in that, while FIGS. 14Aand 14B showed symbols arranged at sequential carriers, FIGS. 16A and16B do not arrange the symbols at sequential carriers. Obviously, forFIGS. 16A and 16B, different reordering methods may be applied to thesymbols of modulated signal z1 and to the symbols of modulated signal z2as in FIGS. 15A and 15B.

FIGS. 17A and 17B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from those of FIGS. 14A through 16B. FIG. 17A illustrates areordering method for the symbols of modulated signal z1 and FIG. 17Billustrates a reordering method for the symbols of modulated signal z2.While FIGS. 14A through 16B show symbols arranged with respect to thefrequency axis, FIGS. 17A and 17B use the frequency and time axestogether in a single arrangement.

While FIG. 69 describes an example where the change of phase isperformed in a four slot period (cycle), the following example describesan eight slot period (cycle). In FIGS. 17A and 17B, the symbol group1702 is equivalent to one period (cycle) of symbols when the phasechanging scheme is used (i.e., to eight symbols) such that symbol #0 isthe symbol obtained by using the phase at timestamp u, symbol #1 is thesymbol obtained by using the phase at timestamp u+1, symbol #2 is thesymbol obtained by using the phase at timestamp u+2, symbol #3 is thesymbol obtained by using the phase at timestamp u+3, symbol #4 is thesymbol obtained by using the phase at timestamp u+4, symbol #5 is thesymbol obtained by using the phase at timestamp u+5, symbol #6 is thesymbol obtained by using the phase at timestamp u+6, and symbol #7 isthe symbol obtained by using the phase at timestamp u+7. Accordingly,for any symbol #x, symbol #x is the symbol obtained by using the phaseat timestamp u when x mod 8 equals 0, symbol #x is the symbol obtainedby using the phase at timestamp u+1 when x mod 8 equals 1, symbol #x isthe symbol obtained by using the phase at timestamp u+2 when x mod 8equals 2, symbol #x is the symbol obtained by using the phase attimestamp u+3 when x mod 8 equals 3, symbol #x is the symbol obtained byusing the phase at timestamp u+4 when x mod 8 equals 4, symbol #x is thesymbol obtained by using the phase at timestamp u+5 when x mod 8 equals5, symbol #x is the symbol obtained by using the phase at timestamp u+6when x mod 8 equals 6, and symbol #x is the symbol obtained by using thephase at timestamp u+7 when x mod 8 equals 7. In FIGS. 17A and 17B fourslots along the time axis and two slots along the frequency axis areused for a total of 4×2=8 slots, in which one period (cycle) of symbolsis arranged. Here, given m×n symbols per period (cycle) (i.e., m×ndifferent phases are available for multiplication), then n slots(carriers) in the frequency domain and m slots in the time domain shouldbe used to arrange the symbols of each period (cycle), such that m>n.This is because the phase of direct waves fluctuates slowly in the timedomain relative to the frequency domain. Accordingly, the presentEmbodiment performs a regular change of phase that reduces the influenceof steady direct waves. Thus, the phase changing period (cycle) shouldpreferably reduce direct wave fluctuations. Accordingly, m should begreater than n. Taking the above into consideration, using the time andfrequency domains together for reordering, as shown in FIGS. 17A and17B, is preferable to using either of the frequency domain or the timedomain alone due to the strong probability of the direct waves becomingregular. As a result, the effects of the present invention are moreeasily obtained. However, reordering in the frequency domain may lead todiversity gain due the fact that frequency-domain fluctuations areabrupt. As such, using the frequency and time domains together forreordering is not always ideal.

FIGS. 18A and 18B indicate frequency on the horizontal axes and time onthe vertical axes thereof, and illustrate an example of a symbolreordering method used by the reorderers 1301A and 1301B from FIG. 13that differs from that of FIGS. 17A and 17B. FIG. 18A illustrates areordering method for the symbols of modulated signal z1, while FIG. 18Billustrates a reordering method for the symbols of modulated signal z2.Much like FIGS. 17A and 17B, FIGS. 18A and 18B illustrate the use of thetime and frequency domains, together. However, in contrast to FIGS. 17Aand 17B, where the frequency domain is prioritized and the time domainis used for secondary symbol arrangement, FIGS. 18A and 18B prioritizethe time domain and use the frequency domain for secondary symbolarrangement. In FIG. 18B, symbol group 1802 corresponds to one period(cycle) of symbols when the phase changing method is used.

In FIGS. 17A, 17B, 18A, and 18B, the reordering method applied to thesymbols of modulated signal z1 and the symbols of modulated signal z2may be identical or may differ as like in FIGS. 15A and 15B. Eitherapproach allows good reception quality to be obtained. Also, in FIGS.17A, 17B, 18A, and 18B, the symbols may be arranged non-sequentially asin FIGS. 16A and 16B. Either approach allows good reception quality tobe obtained.

FIG. 22 indicates frequency on the horizontal axis and time on thevertical axis thereof, and illustrates an example of a symbol reorderingmethod used by the reorderers 1301A and 1301B from FIG. 13 that differsfrom the above. FIG. 22 illustrates a regular phase changing methodusing four slots, similar to timestamps u through u+3 from FIG. 69. Thecharacteristic feature of FIG. 22 is that, although the symbols arereordered with respect to the frequency domain, when read along the timeaxis, a periodic shift of n (n=1 in the example of FIG. 22) symbols isapparent. The frequency-domain symbol group 2210 in FIG. 22 indicatesfour symbols to which are applied the changes of phase at timestamps uthrough u+3 from FIG. 69.

Here, symbol #0 is obtained through a change of phase at timestamp u,symbol #1 is obtained through a change of phase at timestamp u+1, symbol#2 is obtained through a change of phase at timestamp u+2, and symbol #3is obtained through a change of phase at timestamp u+3.

Similarly, for frequency-domain symbol group 2220, symbol #4 is obtainedthrough a change of phase at timestamp u, symbol #5 is obtained througha change of phase at timestamp u+1, symbol #6 is obtained through achange of phase at timestamp u+2, and symbol #7 is obtained through achange of phase at timestamp u+3.

The above-described change of phase is applied to the symbol attimestamp $1. However, in order to apply periodic shifting with respectto the time domain, the following change of phases are applied to symbolgroups 2201, 2202, 2203, and 2204.

For time-domain symbol group 2201, symbol #0 is obtained through achange of phase at timestamp u, symbol #9 is obtained through a changeof phase at timestamp u+1, symbol #18 is obtained through a change ofphase at timestamp u+2, and symbol #27 is obtained through a change ofphase at timestamp u+3.

For time-domain symbol group 2202, symbol #28 is obtained through achange of phase at timestamp u, symbol #1 is obtained through a changeof phase at timestamp u+1, symbol #10 is obtained through a change ofphase at timestamp u+2, and symbol #19 is obtained through a change ofphase at timestamp u+3.

For time-domain symbol group 2203, symbol #20 is obtained through achange of phase at timestamp u, symbol #29 is obtained through a changeof phase at timestamp u+1, symbol #2 is obtained through a change ofphase at timestamp u+2, and symbol #11 is obtained through a change ofphase at timestamp u+3.

For time-domain symbol group 2204, symbol #12 is obtained through achange of phase at timestamp u, symbol #21 is obtained through a changeof phase at timestamp u+1, symbol #30 is obtained through a change ofphase at timestamp u+2, and symbol #3 is obtained through a change ofphase at timestamp u+3.

The characteristic feature of FIG. 22 is seen in that, taking symbol #11as an example, the two neighbouring symbols thereof having the sametimestamp in the frequency domain (#10 and #12) are both symbols changedusing a different phase than symbol #11, and the two neighbouringsymbols thereof having the same carrier in the time domain (#2 and #20)are both symbols changed using a different phase than symbol #11. Thisholds not only for symbol #11, but also for any symbol having twoneighbouring symbols in the frequency domain and the time domain.Accordingly, the change of phase is effectively carried out. This ishighly likely to improve data reception quality as influence fromregularizing direct waves is less prone to reception.

Although FIG. 22 illustrates an example in which n=1, the invention isnot limited in this manner. The same may be applied to a case in whichn=3. Furthermore, although FIG. 22 illustrates the realization of theabove-described effects by arranging the symbols in the frequency domainand advancing in the time domain so as to achieve the characteristiceffect of imparting a periodic shift to the symbol arrangement order,the symbols may also be randomly (or regularly) arranged to the sameeffect.

Although the present Embodiment describes a variation of Embodiment 1 inwhich a baseband signal switcher is inserted before the change of phase,the present Embodiment may also be realized as a combination withEmbodiment 2, such that the baseband signal switcher is inserted beforethe change of phase in FIGS. 26 and 28. Accordingly, in FIG. 26, phasechanger 317A takes switched baseband signal 6701A(q₁(i)) as input, andphase changer 317B takes switched baseband signal 6701B(q₂(i)) as input.The same applies to the phase changers 317A and 317B from FIG. 28.

The following describes a method of allowing the reception device toobtain good received signal quality for data, regardless of thereception device arrangement, by considering the location of thereception device with respect to the transmission device.

FIG. 31 illustrates an example of frame configuration for a portion ofthe symbols within a signal in the time-frequency domains, given atransmission method where a regular change of phase is performed for amulti-carrier method such as OFDM.

FIG. 31 illustrates the frame configuration of modulated signal z2′corresponding to the switched baseband signal input to phase changer317B from FIG. 67. Each square represents one symbol (although bothsignals s1 and s2 are included for precoding purposes, depending on theprecoding matrix, only one of signals s1 and s2 may be used).

Consider symbol 3100 at carrier 2 and timestamp $2 of FIG. 31. Thecarrier here described may alternatively be termed a sub-carrier.

Within carrier 2, there is a very strong correlation between the channelconditions for symbol 3100A at carrier 2, timestamp $2 and the channelconditions for the time domain nearest-neighbour symbols to timestamp$2, i.e., symbol 3013 at timestamp $1 and symbol 3101 at timestamp $3within carrier 2.

Similarly, for timestamp $2, there is a very strong correlation betweenthe channel conditions for symbol 3100 at carrier 2, timestamp $2 andthe channel conditions for the frequency-domain nearest-neighboursymbols to carrier 2, i.e., symbol 3104 at carrier 1, timestamp $2 andsymbol 3104 at timestamp $2, carrier 3.

As described above, there is a very strong correlation between thechannel conditions for symbol 3100 and the channel conditions for eachsymbol 3101, 3102, 3103, and 3104.

The present description considers N different phases (N being aninteger, N≧2) for multiplication in a transmission method where thephase is regularly changed. The symbols illustrated in FIG. 31 areindicated as e^(j0), for example. This signifies that this symbol issignal z2′ from FIG. 6 having undergone a change in phase throughmultiplication by e^(j0). That is, the values given for the symbols inFIG. 31 are the value of y(t) as given by Math. 70 (formula 70).

The present Embodiment takes advantage of the high correlation inchannel conditions existing between neighbouring symbols in thefrequency domain and/or neighbouring symbols in the time domain in asymbol arrangement enabling high data reception quality to be obtainedby the reception device receiving the post-phase change symbols.

In order to achieve this high data reception quality, conditions #D1-1and #D1-2 are met.

(Condition #D1-1)

As shown in FIG. 69, for a transmission method involving a regularchange of phase performed on switched baseband signal q2 using amulti-carrier method such as OFDM, time X, carrier Y is a symbol fortransmitting data (hereinafter, data symbol), neighbouring symbols inthe time domain, i.e., at time X−1, carrier Y and at time X+1, carrier Yare also data symbols, and a different change of phase should beperformed on switched baseband signal q2 corresponding to each of thesethree data symbols, i.e., on switched baseband signal q2 at time X,carrier Y, at time X−1, carrier Y and at time X+1, carrier Y.

(Condition #D1-2)

As shown in FIG. 69, for a transmission method involving a regularchange of phase performed on switched baseband signal q2 using amulti-carrier method such as OFDM, time X, carrier Y is a symbol fortransmitting data (hereinafter, data symbol), neighbouring symbols inthe time domain, i.e., at time X, carrier Y+1 and at time X, carrier Y−1are also data symbols, and a different change of phase should beperformed on switched baseband signal q2 corresponding to each of thesethree data symbols, i.e., on switched baseband signal q2 at time X,carrier Y, at time X, carrier Y−1 and at time X, carrier Y+1.

Ideally, a data symbol should satisfy Condition #D1-1. Similarly, thedata symbols should satisfy Condition #D1-2.

The reasons supporting Conditions #D1-1 and #D1-2 are as follows.

A very strong correlation exists between the channel conditions of givensymbol of a transmit signal (hereinafter, symbol A) and the channelconditions of the symbols neighbouring symbol A in the time domain, asdescribed above.

Accordingly, when three neighbouring symbols in the time domain eachhave different phases, then despite reception quality degradation in theLOS environment (poor signal quality caused by degradation in conditionsdue to phase relations despite high signal quality in terms of SNR) forsymbol A, the two remaining symbols neighbouring symbol A are highlylikely to provide good reception quality. As a result, good receivedsignal quality is achievable after error correction and decoding.

Similarly, a very strong correlation exists between the channelconditions of given symbol of a transmit signal (symbol A) and thechannel conditions of the symbols neighbouring symbol A in the frequencydomain, as described above.

Accordingly, when three neighbouring symbols in the frequency domaineach have different phases, then despite reception quality degradationin the LOS environment (poor signal quality caused by degradation inconditions due to direct wave phase relationships despite high signalquality in terms of SNR) for symbol A, the two remaining symbolsneighbouring symbol A are highly likely to provide good receptionquality. As a result, good received signal quality is achievable aftererror correction and decoding.

By combining Conditions #D1-1 and #D1-2, ever greater data receptionquality is likely achievable for the reception device. Accordingly, thefollowing Condition #D1-3 can be derived.

(Condition #D1-3)

As shown in FIG. 69, for a transmission method involving a regularchange of phase performed on switched baseband signal q2 using amulti-carrier method such as OFDM, time X, carrier Y is a symbol fortransmitting data (data symbol), neighbouring symbols in the timedomain, i.e., at time X−1, carrier Y and at time X+1, carrier Y are alsodata symbols, and neighbouring symbols in the frequency domain, i.e., attime X, carrier Y−1 and at time X, carrier Y+1 are also data symbols,such that a different change of phase should be performed on switchedbaseband signal q2 corresponding to each of these five data symbols,i.e., on switched baseband signal q2 at time X, carrier Y, at time X,carrier Y−1, at time X, carrier Y+1, at time X−1, carrier Y and at timeX+1, carrier Y.

Here, the different changes in phase are as follows. Phase changes aredefined from 0 radians to 2π radians. For example, for time X, carrierY, a phase change of e^(jθX,Y) is applied to precoded baseband signal q₂from FIG. 69, for time X−1, carrier Y, a phase change of e^(jθX−1,Y) isapplied to precoded baseband signal q2 from FIG. 69, for time X+1,carrier Y, a phase change of e^(jθX+1,Y) is applied to precoded basebandsignal q2 from FIG. 69, such that 0≦θ_(X,Y)<2π, 0≦θ_(X−1,Y)<2π, and0≦θ_(X+1,Y)<2π, all units being in radians. Accordingly, for Condition#D1-1, it follows that θ_(X,Y)≠θ_(X,Y−1), θ_(X,Y)≠θ_(X,Y+1), and thatθ_(X,Y−1)≠θ_(X,Y+1). Similarly, for Condition #D1-2, it follows thatθ_(X,Y)≠θ_(X,Y−1), θ_(X,Y)≠θ_(X,Y+1), and that θ_(X,Y−1)≠θ_(X,Y+1). And,for Condition #D1-3, it follows that θ_(X,Y)≠θ_(X−1,Y),θ_(X,Y)≠θ_(X+1,Y), θ_(X,Y)≠θ_(X,Y−1), θ_(X,Y)≠θ_(X,Y+1),θ_(X−1,Y)≠θ_(X+1,Y), θ_(X−1,Y)≠θ_(X,Y)−1, θ_(X−1,Y)≠θ_(X,Y+1),θ_(X+1,Y)≠θ_(X,Y−1), θ_(X+1,Y)≠θ_(X,Y+1), and that θ_(X,Y−1)≠θ_(X,Y+1).

Ideally, a data symbol should satisfy Condition #D1-3.

FIG. 31 illustrates an example of Condition #D1-3, where symbol Acorresponds to symbol 3100. The symbols are arranged such that the phaseby which switched baseband signal q2 from FIG. 69 is multiplied differsfor symbol 3100, for both neighbouring symbols thereof in the timedomain 3101 and 3102, and for both neighbouring symbols thereof in thefrequency domain 3102 and 3104. Accordingly, despite received signalquality degradation of symbol 3100 for the receiver, good signal qualityis highly likely for the neighbouring signals, thus guaranteeing goodsignal quality after error correction.

FIG. 32 illustrates a symbol arrangement obtained through phase changesunder these conditions.

As evident from FIG. 32, with respect to any data symbol, a differentchange in phase is applied to each neighbouring symbol in the timedomain and in the frequency domain. As such, the ability of thereception device to correct errors may be improved.

In other words, in FIG. 32, when all neighbouring symbols in the timedomain are data symbols, Condition #D1-1 is satisfied for all Xs and allYs.

Similarly, in FIG. 32, when all neighbouring symbols in the frequencydomain are data symbols, Condition #D1-2 is satisfied for all Xs and allYs.

Similarly, in FIG. 32, when all neighbouring symbols in the frequencydomain are data symbols and all neighbouring symbols in the time domainare data symbols, Condition #D1-3 is satisfied for all Xs and all Ys.

The following discusses the above-described example for a case where thechange of phase is performed on two switched baseband signals q1 and q2(see FIG. 68).

Several phase changing methods are applicable to performing a change ofphase on two switched baseband signals q1 and q2. The details thereofare explained below.

Scheme 1 involves a change in phase of switched baseband signal q2 asdescribed above, to achieve the change in phase illustrated by FIG. 32.In FIG. 32, a change of phase having a period (cycle) of ten is appliedto switched baseband signal q2. However, as described above, in order tosatisfy Conditions #D1-1, #D1-2, and #D1-3, the change in phase appliedto switched baseband signal q2 at each (sub-)carrier changes over time.(Although such changes are applied in FIG. 32 with a period (cycle) often, other phase changing methods are also applicable.) Then, as shownin FIG. 33, the phase change degree performed on switched basebandsignal q2 produce a constant value that is one-tenth that of the changein phase performed on switched baseband signal q2. In FIG. 33, for aperiod (cycle) (of phase change performed on switched baseband signalq2) including timestamp $1, the value of the change in phase performedon switched baseband signal q1 is e^(j0). Then, for the next period(cycle) (of change in phase performed on switched baseband signal q2)including timestamp $2, the value of the phase changing degree performedon precoded baseband signal q1 is e^(jπ/9), and so on.

The symbols illustrated in FIG. 33 are indicated as e^(j0), for example.This signifies that this symbol is signal q1 from FIG. 26 havingundergone a change of phase through multiplication by e^(j0).

As shown in FIG. 33, the change in phase applied to switched basebandsignal q1 produces a constant value that is one-tenth that of the changein phase performed on precoded, switched baseband signal q2 such thatthe post-phase change value varies with the number of each period(cycle). (As described above, in FIG. 33, the value is e^(j0) for thefirst period (cycle), e^(jπ/9) for the second period (cycle), and soon.)

As described above, the change in phase performed on switched basebandsignal q2 has a period (cycle) of ten, but the period (cycle) can beeffectively made greater than ten by taking the degree of phase changeapplied to switched baseband signal q1 and to switched baseband signalq2 into consideration. Accordingly, data reception quality may beimproved for the reception device.

Scheme 2 involves a change in phase of switched baseband signal q2 asdescribed above, to achieve the change in phase illustrated by FIG. 32.In FIG. 32, a change of phase having a period (cycle) of ten is appliedto switched baseband signal q2. However, as described above, in order tosatisfy Conditions #D1-1, #D1-2, and #D1-3, the change in phase appliedto switched baseband signal q2 at each (sub-)carrier changes over time.(Although such changes are applied in FIG. 32 with a period (cycle) often, other phase changing methods are also applicable.) Then, as shownin FIG. 33, the change in phase performed on switched baseband signal q2produces a constant value that is one-tenth of that performed onswitched baseband signal q2.

The symbols illustrated in FIG. 30 are indicated as e^(j0), for example.This signifies that this symbol is switched baseband signal q1 havingundergone a change of phase through multiplication by e^(j0).

As described above, the change in phase performed on switched basebandsignal q2 has a period (cycle) of ten, but the period (cycle) can beeffectively made greater than ten by taking the changes in phase appliedto switched baseband signal q1 and to switched baseband signal q2 intoconsideration. Accordingly, data reception quality may be improved forthe reception device. An effective way of applying method 2 is toperform a change in phase on switched baseband signal q1 with a period(cycle) of N and perform a change in phase on precoded baseband signalq2 with a period (cycle) of M such that N and M are coprime. As such, bytaking both switched baseband signals q1 and q2 into consideration, aperiod (cycle) of N×M is easily achievable, effectively making theperiod (cycle) greater when N and M are coprime.

While the above discusses an example of the above-described phasechanging method, the present invention is not limited in this manner.The change in phase may be performed with respect to the frequencydomain, the time domain, or on time-frequency blocks. Similarimprovement to the data reception quality can be obtained for thereception device in all cases.

The same also applies to frames having a configuration other than thatdescribed above, where pilot symbols (SP symbols) and symbolstransmitting control information are inserted among the data symbols.The details of the change in phase in such circumstances are as follows.

FIGS. 47A and 47B illustrate the frame configuration of modulatedsignals (switched baseband signals q1 and q2) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 47A illustrates the frame configuration ofmodulated signal (switched baseband signal q1) z1 or z1′ while FIG. 47Billustrates the frame configuration of modulated signal (switchedbaseband signal q2) z2′. In FIGS. 47A and 47B, 4701 marks pilot symbolswhile 4702 marks data symbols. The data symbols 4702 are symbols onwhich switching or switching and change in phase have been performed.

FIGS. 47A and 47B, like FIG. 69, indicate the arrangement of symbolswhen a change in phase is applied to switched baseband signal q2 (whileno change in phase is performed on switched baseband signal q1).(Although FIG. 69 illustrates a change in phase with respect to the timedomain, switching time t with carrier f in FIG. 69 corresponds to achange in phase with respect to the frequency domain. In other words,replacing (t) with (t, f) where t is time and f is frequency correspondsto performing a change of phase on time-frequency blocks.) Accordingly,the numerical values indicated in FIGS. 47A and 47B for each of thesymbols are the values of switched baseband signal q2 after the changein phase. No values are given for the symbols of switched basebandsignal q1(z1) from FIGS. 47A and 47B as no change in phase is performedthereon.

The important point of FIGS. 47A and 47B is that the change in phaseperformed on the data symbols of switched baseband signal q2, i.e., onsymbols having undergone precoding or precoding and switching. (Thesymbols under discussion, being precoded, actually include both symbolss1 and s2.) Accordingly, no change in phase is performed on the pilotsymbols inserted in z2′.

FIGS. 48A and 48B illustrate the frame configuration of modulatedsignals (switched baseband signals q1 and q2) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 48A illustrates the frame configuration ofmodulated signal (switched baseband signal q1) z1 or z1′ while FIG. 48Billustrates the frame configuration of modulated signal (switchedbaseband signal q2) z2′. In FIGS. 48A and 48B, 4701 marks pilot symbolswhile 4702 marks data symbols. The data symbols 4702 are symbols onwhich precoding or precoding and a change in phase have been performed.

FIGS. 48A and 48B indicate the arrangement of symbols when a change inphase is applied to switched baseband signal q1 and to switched basebandsignal q2. Accordingly, the numerical values indicated in FIGS. 48A and48B for each of the symbols are the values of switched baseband signalsq1 and q2 after a change in phase.

The important point of FIGS. 48A and 48B is that the change in phase isperformed on the data symbols of switched baseband signal q1, that is,on the precoded or precoded and switched symbols thereof, and on thedata symbols of switched baseband signal q2, that is, on the precoded orprecoded and switched symbols thereof. (The symbols under discussion,being precoded, actually include both symbols s1 and s2.) Accordingly,no change in phase is performed on the pilot symbols inserted in z1′,nor on the pilot symbols inserted in z2′.

FIGS. 49A and 49B illustrate the frame configuration of modulatedsignals (switched baseband signals q1 and q2) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 49A illustrates the frame configuration ofmodulated signal (switched baseband signal q1) z1 or z1′ while FIG. 49Billustrates the frame configuration of modulated signal (switchedbaseband signal q2) z2′. In FIGS. 49A and 49B, 4701 marks pilot symbols,4702 marks data symbols, and 4901 marks null symbols for which thein-phase component of the baseband signal I=0 and the quadraturecomponent Q=0. As such, data symbols 4702 are symbols on which precodingor precoding and a change in phase have been performed. FIGS. 49A and49B differ from FIGS. 47A and 47B in the configuration scheme forsymbols other than data symbols. The times and carriers at which pilotsymbols are inserted into modulated signal z1′ are null symbols inmodulated signal z2′. Conversely, the times and carriers at which pilotsymbols are inserted into modulated signal z2′ are null symbols inmodulated signal z1′.

FIGS. 49A and 49B, like FIG. 69, indicate the arrangement of symbolswhen a change in phase is applied to switched baseband signal q2 (whileno change in phase is performed on switched baseband signal q1).(Although FIG. 69 illustrates a change in phase with respect to the timedomain, switching time t with carrier f in FIG. 6 corresponds to achange in phase with respect to the frequency domain. In other words,replacing (t) with (t, f) where t is time and f is frequency correspondsto performing a change of phase on time-frequency blocks.) Accordingly,the numerical values indicated in FIGS. 49A and 49B for each of thesymbols are the values of switched baseband signal q2 after the changein phase. No values are given for the symbols of switched basebandsignal q1 from FIGS. 49A and 49B as no change in phase is performedthereon.

The important point of FIGS. 49A and 49B is that the change in phaseperformed on the data symbols of switched baseband signal q2, i.e., onsymbols having undergone precoding or precoding and switching. (Thesymbols under discussion, being precoded, actually include both symbolss1 and s2.) Accordingly, no change in phase is performed on the pilotsymbols inserted in z2′.

FIGS. 50A and 50B illustrate the frame configuration of modulatedsignals (switched baseband signals q1 and q2) z1 or z1′ and z2′ in thetime-frequency domain. FIG. 50A illustrates the frame configuration ofmodulated signal (switched baseband signal q1) z1 or z1′ while FIG. 50Billustrates the frame configuration of modulated signal (switchedbaseband signal q2) z2′. In FIGS. 50A and 50B, 4701 marks pilot symbols,4702 marks data symbols, and 4901 marks null symbols for which thein-phase component of the baseband signal I=0 and the quadraturecomponent Q=0. As such, data symbols 4702 are symbols on which precodingor precoding and a change in phase have been performed. FIGS. 50A and50B differ from FIGS. 48A and 48B in the configuration scheme forsymbols other than data symbols. The times and carriers at which pilotsymbols are inserted into modulated signal z1′ are null symbols inmodulated signal z2′. Conversely, the times and carriers at which pilotsymbols are inserted into modulated signal z2′ are null symbols inmodulated signal z1′.

FIGS. 50A and 50B indicate the arrangement of symbols when a change inphase is applied to switched baseband signal q1 and to switched basebandsignal q2. Accordingly, the numerical values indicated in FIGS. 50A and50B for each of the symbols are the values of switched baseband signalsq1 and q2 after a change in phase.

The important point of FIGS. 50A and 50B is that a change in phase isperformed on the data symbols of switched baseband signal q1, that is,on the precoded or precoded and switched symbols thereof, and on thedata symbols of switched baseband signal q2, that is, on the precoded orprecoded and switched symbols thereof. (The symbols under discussion,being precoded, actually include both symbols s1 and s2.) Accordingly,no change in phase is performed on the pilot symbols inserted in z1′,nor on the pilot symbols inserted in z2′.

FIG. 51 illustrates a sample configuration of a transmission devicegenerating and transmitting modulated signal having the frameconfiguration of FIGS. 47A, 47B, 49A, and 49B. Components thereofperforming the same operations as those of FIG. 4 use the same referencesymbols thereas. FIG. 51 does not include a baseband signal switcher asillustrated in FIGS. 67 and 70. However, FIG. 51 may also include abaseband signal switcher between the weighting unit and phase changer,much like FIGS. 67 and 70.

In FIG. 51, the weighting units 308A and 308B, phase changer 317B, andbaseband signal switcher only operate at times indicated by the frameconfiguration signal 313 as corresponding to data symbols.

In FIG. 51, a pilot symbol generator 5101 (that also generates nullsymbols) outputs baseband signals 5102A and 5102B for a pilot symbolwhenever the frame configuration signal 313 indicates a pilot symbol(and a null symbol).

Although not indicated in the frame configurations from FIGS. 47Athrough 50B, when precoding (and phase rotation) is not performed, suchas when transmitting a modulated signal using only one antenna (suchthat the other antenna transmits no signal) or when using a space-timecoding transmission method (particularly, space-time block coding) totransmit control information symbols, then the frame configurationsignal 313 takes control information symbols 5104 and controlinformation 5103 as input. When the frame configuration signal 313indicates a control information symbol, baseband signals 5102A and 5102Bthereof are output.

Wireless units 310A and 310B of FIG. 51 take a plurality of basebandsignals as input and select a desired baseband signal according to theframe configuration signal 313. The wireless units 310A and 310B thenapply OFDM signal processing and output modulated signals 311A and 311Bconforming to the frame configuration.

FIG. 52 illustrates a sample configuration of a transmission devicegenerating and transmitting modulated signal having the frameconfiguration of FIGS. 48A, 48B, 50A, and 50B. Components thereofperforming the same operations as those of FIGS. 4 and 51 use the samereference symbols thereas. FIG. 52 features an additional phase changer317A that only operates when the frame configuration signal 313indicates a data symbol. At all other times, the operations areidentical to those explained for FIG. 51. FIG. 52 does not include abaseband signal switcher as illustrated in FIGS. 67 and 70. However,FIG. 52 may also include a baseband signal switcher between theweighting unit and phase changer, much like FIGS. 67 and 70.

FIG. 53 illustrates a sample configuration of a transmission device thatdiffers from that of FIG. 51. FIG. 53 does not include a baseband signalswitcher as illustrated in FIGS. 67 and 70. However, FIG. 53 may alsoinclude a baseband signal switcher between the weighting unit and phasechanger, much like FIGS. 67 and 70. The following describes the pointsof difference. As shown in FIG. 53, phase changer 317B takes a pluralityof baseband signals as input. Then, when the frame configuration signal313 indicates a data symbol, phase changer 317B performs the change inphase on precoded baseband signal 316B. When frame configuration signal313 indicates a pilot symbol (or null symbol) or a control informationsymbol, phase changer 317B pauses phase changing operations such thatthe symbols of the baseband signal are output as-is. (This may beinterpreted as performing forced rotation corresponding to e^(j0).)

A selector 5301 takes the plurality of baseband signals as input andselects a baseband signal having a symbol indicated by the frameconfiguration signal 313 for output.

FIG. 54 illustrates a sample configuration of a transmission device thatdiffers from that of FIG. 52. FIG. 54 does not include a baseband signalswitcher as illustrated in FIGS. 67 and 70. However, FIG. 54 may alsoinclude a baseband signal switcher between the weighting unit and phasechanger, much like FIGS. 67 and 70. The following describes the pointsof difference. As shown in FIG. 54, phase changer 317B takes a pluralityof baseband signals as input. Then, when the frame configuration signal313 indicates a data symbol, phase changer 317B performs the change inphase on precoded baseband signal 316B. When frame configuration signal313 indicates a pilot symbol (or null symbol) or a control informationsymbol, phase changer 317B pauses phase changing operations such thatthe symbols of the baseband signal are output as-is. (This may beinterpreted as performing forced rotation corresponding to e^(j0).)

Similarly, as shown in FIG. 54, phase changer 5201 takes a plurality ofbaseband signals as input. Then, when the frame configuration signal 313indicates a data symbol, phase changer 5201 performs the change in phaseon precoded baseband signal 309A. When frame configuration signal 313indicates a pilot symbol (or null symbol) or a control informationsymbol, phase changer 5201 pauses phase changing operations such thatthe symbols of the baseband signal are output as-is. (This may beinterpreted as performing forced rotation corresponding to e^(j0).)

The above explanations are given using pilot symbols, control symbols,and data symbols as examples. However, the present invention is notlimited in this manner. When symbols are transmitted using methods otherthan precoding, such as single-antenna transmission or transmissionusing space-time block coding, the absence of change in phase isimportant. Conversely, performing the change of phase on symbols thathave been precoded is the key point of the present invention.

Accordingly, a characteristic feature of the present invention is thatthe change in phase is not performed on all symbols within the frameconfiguration in the time-frequency domain, but only performed onbaseband signals that have been precoded and have undergone switching.

The following describes a scheme for regularly changing the phase whenencoding is performed using block codes as described in Non-PatentLiterature 12 through 15, such as QC LDPC Codes (not only QC-LDPC butalso LDPC codes may be used), concatenated LDPC and BCH codes, Turbocodes or Duo-Binary Turbo codes using tail-biting, and so on. Thefollowing example considers a case where two streams s1 and s2 aretransmitted. When encoding has been performed using block codes andcontrol information and the like is not necessary, the number of bitsmaking up each coded block matches the number of bits making up eachblock code (control information and so on described below may yet beincluded). When encoding has been performed using block codes or thelike and control information or the like (e.g., CRC transmissionparameters) is required, then the number of bits making up each codedblock is the sum of the number of bits making up the block codes and thenumber of bits making up the information.

FIG. 34 illustrates the varying numbers of symbols and slots needed intwo coded blocks when block codes are used. Unlike FIGS. 69 and 70, forexample, FIG. 34 illustrates the varying numbers of symbols and slotsneeded in each coded block when block codes are used when, for example,two streams s1 and s2 are transmitted as indicated in FIG. 4, with anencoder and distributor. (Here, the transmission method may be anysingle-carrier method or multi-carrier method such as OFDM.)

As shown in FIG. 34, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

Then, given that the above-described transmission device transmits twostreams simultaneously, 1500 of the aforementioned 3000 symbols neededwhen the modulation scheme is QPSK are assigned to s1 and the other 1500symbols are assigned to s2. As such, 1500 slots for transmitting the1500 symbols (hereinafter, slots) are required for each of s1 and s2.

By the same reasoning, when the modulation scheme is 16-QAM, 750 slotsare needed to transmit all of the bits making up two coded blocks, andwhen the modulation scheme is 64-QAM, 500 slots are needed to transmitall of the bits making up the two coded blocks.

The following describes the relationship between the above-defined slotsand the phase of multiplication, as pertains to methods for a regularchange of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase. That is, the phase changer of the above-describedtransmission device uses five phase changing values (or phase changingsets) to achieve the period (cycle) of five. (As in FIG. 69, five phasechanging values are needed in order to perform a change of phase havinga period (cycle) of five on switched baseband signal q2 only. Similarly,in order to perform the change in phase on both switched basebandsignals q1 and q2, two phase changing values are needed for each slot.These two phase changing values are termed a phase changing set.Accordingly, here, in order to perform a change of phase having a period(cycle) of five, five such phase changing sets should be prepared). Thefive phase changing values (or phase changing sets) are expressed asPHASE[0], PHASE[1], PHASE[2], PHASE[3], and PHASE [4].

For the above-described 1500 slots needed to transmit the 6000 bitsmaking up a single coded block when the modulation scheme is QPSK,PHASE[0] is used on 300 slots, PHASE[1] is used on 300 slots, PHASE[2]is used on 300 slots, PHASE[3] is used on 300 slots, and PHASE[4] isused on 300 slots. This is due to the fact that any bias in phase usagecauses great influence to be exerted by the more frequently used phase,and that the reception device is dependent on such influence for datareception quality.

Furthermore, for the above-described 750 slots needed to transmit the6000 bits making up a single coded block when the modulation scheme is16-QAM, PHASE[0] is used on 150 slots, PHASE[1] is used on 150 slots,PHASE[2] is used on 150 slots, PHASE[3] is used on 150 slots, andPHASE[4] is used on 150 slots.

Further still, for the above-described 500 slots needed to transmit the6000 bits making up a single coded block when the modulation scheme is64-QAM, PHASE[0] is used on 100 slots, PHASE[1] is used on 100 slots,PHASE[2] is used on 100 slots, PHASE[3] is used on 100 slots, andPHASE[4] is used on 100 slots.

As described above, a scheme for a regular change of phase requires thepreparation of N phase changing values (or phase changing sets) (wherethe N different phases are expressed as PHASE[0], PHASE[1], PHASE[2] . .. PHASE[N−2], PHASE[N−1]). As such, in order to transmit all of the bitsmaking up a single coded block, PHASE[0] is used on K₀ slots, PHASE[1]is used on K₁ slots, PHASE[i] is used on K_(i) slots (where i=0, 1, 2 .. . N−1 (i being an integer between 0 and N−1)), and PHASE[N−1] is usedon K_(N−1) slots, such that Condition #D1-4 is met.

(Condition #D1-4)

K₀=K₁ . . . =K_(i)= . . . K_(N−1). That is, K_(a)=K_(b) (for ∀a and ∀bwhere a, b,=0, 1, 2 . . . N−1 (a and b being integers between 0 andN−1), a≠b).

Then, when a communication system that supports multiple modulationschemes selects one such supported method for use, Conditions #D1-4 ispreferably met for the supported modulation scheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #D1-4 may not be satisfied for some modulation schemes. Insuch a case, the following condition applies instead of Condition #D1-4.

(Condition #D1-5)

The difference between K_(a) and K_(b) satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (aand b being integers between 0 and N−1), a≠b)

FIG. 35 illustrates the varying numbers of symbols and slots needed intwo coded blocks when block codes are used. FIG. 35 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the transmission device from FIG. 67 andFIG. 70, and the transmission device has two encoders. (Here, thetransmission method may be any single-carrier method or multi-carriermethod such as OFDM.)

As shown in FIG. 35, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

The transmission device from FIG. 67 and the transmission device fromFIG. 70 each transmit two streams at once, and have two encoders. Assuch, the two streams each transmit different code blocks. Accordingly,when the modulation scheme is QPSK, two coded blocks drawn from s1 ands2 are transmitted within the same interval, e.g., a first coded blockdrawn from s1 is transmitted, then a second coded block drawn from s2 istransmitted. As such, 3000 slots are needed in order to transmit thefirst and second coded blocks.

By the same reasoning, when the modulation scheme is 16-QAM, 1500 slotsare needed to transmit all of the bits making up the two coded blocks,and when the modulation scheme is 64-QAM, 1000 slots are needed totransmit all of the bits making up the two coded blocks

The following describes the relationship between the above-defined slotsand the phase of multiplication, as pertains to methods for a regularchange of phase.

Here, five different phase changing values (or phase changing sets) areassumed as having been prepared for use in the method for a regularchange of phase.

That is, the phase changer of the transmission device from FIG. 67 andFIG. 70 uses five phase changing values (or phase changing sets) toachieve the period (cycle) of five. (As in FIG. 69, five phase changingvalues are needed in order to perform a change of phase having a period(cycle) of five on switched baseband signal q2 only. Similarly, in orderto perform the change in phase on both switched baseband signals q1 andq2, two phase changing values are needed for each slot. These two phasechanging values are termed a phase changing set. Accordingly, here, inorder to perform a change of phase having a period (cycle) of five, fivesuch phase changing sets should be prepared). The five phase changingvalues (or phase changing sets) are expressed as PHASE[0], PHASE[1],PHASE[2], PHASE[3], and PHASE [4].

For the above-described 3000 slots needed to transmit the 6000×2 bitsmaking up the two coded blocks when the modulation scheme is QPSK,PHASE[0] is used on 600 slots, PHASE[1] is used on 600 slots, PHASE[2]is used on 600 slots, PHASE[3] is used on 600 slots, and PHASE[4] isused on 600 slots. This is due to the fact that any bias in phase usagecauses great influence to be exerted by the more frequently used phase,and that the reception device is dependent on such influence for datareception quality.

Furthermore, in order to transmit the first coded block, PHASE[0] isused on slots 600 times, PHASE[1] is used on slots 600 times, PHASE[2]is used on slots 600 times, PHASE[3] is used on slots 600 times, andPHASE[4] is used on slots 600 times. Furthermore, in order to transmitthe second coded block, PHASE[0] is used on slots 600 times, PHASE[1] isused on slots 600 times, PHASE[2] is used on slots 600 times, PHASE[3]is used on slots 600 times, and PHASE[4] is used on slots 600 times.

Similarly, for the above-described 1500 slots needed to transmit the6000×2 bits making up the two coded blocks when the modulation scheme is16-QAM, PHASE[0] is used on 300 slots, PHASE[1] is used on 300 slots,PHASE[2] is used on 300 slots, PHASE[3] is used on 300 slots, andPHASE[4] is used on 300 slots.

Furthermore, in order to transmit the first coded block, PHASE[0] isused on slots 300 times, PHASE[1] is used on slots 300 times, PHASE[2]is used on slots 300 times, PHASE[3] is used on slots 300 times, andPHASE[4] is used on slots 300 times. Furthermore, in order to transmitthe second coded block, PHASE[0] is used on slots 300 times, PHASE[1] isused on slots 300 times, PHASE[2] is used on slots 300 times, PHASE[3]is used on slots 300 times, and PHASE[4] is used on slots 300 times.

Similarly, for the above-described 1000 slots needed to transmit the6000×2 bits making up the two coded blocks when the modulation scheme is64-QAM, PHASE[0] is used on 200 slots, PHASE[1] is used on 200 slots,PHASE[2] is used on 200 slots, PHASE[3] is used on 200 slots, andPHASE[4] is used on 200 slots.

Furthermore, in order to transmit the first coded block, PHASE[0] isused on slots 200 times, PHASE[1] is used on slots 200 times, PHASE[2]is used on slots 200 times, PHASE[3] is used on slots 200 times, andPHASE[4] is used on slots 200 times. Furthermore, in order to transmitthe second coded block, PHASE[0] is used on slots 200 times, PHASE[1] isused on slots 200 times, PHASE[2] is used on slots 200 times, PHASE[3]is used on slots 200 times, and PHASE[4] is used on slots 200 times.

As described above, a method for a regular change of phase requires thepreparation of N phase changing values (or phase changing sets) (wherethe N different phases are expressed as PHASE[0], PHASE[1], PHASE[2] . .. PHASE[N−2], PHASE[N−2]). As such, in order to transmit all of the bitsmaking up a single coded block, PHASE[0] is used on K₀ slots, PHASE[1]is used on K₁ slots, PHASE[i] is used on K_(i) slots (where i=0, 1, 2 .. . N−1 (i being an integer between 0 and N−1)), and PHASE[N−1] is usedon K_(N−1) slots, such that Condition #D1-6 is met.

(Condition #D1-6)

K₀=K₁ . . . =K_(i)= . . . K_(N−1). That is, K_(a)=K_(b) (for ∀a and ∀bwhere a, b,=0, 1, 2 . . . N−1 (a and b being integers between 0 andN−1), a≠b).Further, in order to transmit all of the bits making up the first codedblock, PHASE[0] is used K_(0,1) times, PHASE[1] is used K₁₁ times,PHASE[i] is used K_(i,1) times (where i=0, 1, 2 . . . N−1 (i being aninteger between 0 and N−1)), and PHASE[N−1] is used K_(N−1,1) times,such that Condition #D1-7 is met.

(Condition #D1-7)

K_(0,1)=K_(1,1)= . . . K_(i,1)= . . . K_(N−1,1). That is,K_(a,1)=K_(b,1) (∀a and ∀b where a, b,=0, 1, 2 . . . N−1 (a and b beingintegers between 0 and N−1), a≠b).Furthermore, in order to transmit all of the bits making up the secondcoded block, PHASE[0] is used K_(0,2) times, PHASE[1] is used K_(1,2)times, PHASE[i] is used K_(i,2) times (where i=0, 1, 2 . . . N−1 (ibeing an integer between 0 and N−1)), and PHASE[N−1] is used K_(N−1,2)times, such that Condition #D1-8 is met.

(Condition #D1-8)

K_(0,2)=K_(1,2)= . . . K_(i,2)= . . . K_(N−1,2). That is,K_(a,2)=K_(b,2) (∀a and ∀b where a, b,=0, 1, 2 . . . N−1 (a and b beingintegers between 0 and N−1), a≠b).

Then, when a communication system that supports multiple modulationschemes selects one such supported method for use, Condition #D1-6Condition #D1-7, and Condition #D1-8 is met for the supported modulationscheme.

However, when multiple modulation schemes are supported, each suchmodulation scheme typically uses symbols transmitting a different numberof bits per symbols (though some may happen to use the same number),Condition #D1-6 Condition #D1-7, and Condition #D1-8 may not besatisfied for some modulation schemes. In such a case, the followingconditions apply instead of Condition #D1-6 Condition #D1-7, andCondition #D1-8.

(Condition #D1-9)

The difference between Ka and Kb satisfies 0 or 1. That is,|K_(a)−K_(b)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1 (aand b being integers between 0 and N−1), a≠b)

(Condition #D1-10)

The difference between K_(a,1) and K_(b,1) satisfies 0 or 1. That is,|K_(a,1)−K_(b,1)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1(a and b being integers between 0 and N−1), a≠b)

(Condition #D1-11)

The difference between K_(a,2) and K_(b,2) satisfies 0 or 1. That is,|K_(a,2)−K_(b,2)| satisfies 0 or 1 (∀a, ∀b, where a, b=0, 1, 2 . . . N−1(a and b being integers between 0 and N−1), a≠b)

As described above, bias among the phases being used to transmit thecoded blocks is removed by creating a relationship between the codedblock and the phase of multiplication. As such, data reception qualitymay be improved for the reception device.

As described above, N phase changing values (or phase changing sets) areneeded in order to perform a change of phase having a period (cycle) ofN with the method for the regular change of phase. As such, N phasechanging values (or phase changing sets) PHASE[0], PHASE[1], PHASE[2] .. . PHASE[N−2], and PHASE[N−1] are prepared. However, schemes exist forordering the phases in the stated order with respect to the frequencydomain. No limitation is intended in this regard. The N phase changingvalues (or phase changing sets) PHASE[0], PHASE[1], PHASE[2] . . .PHASE[N−2], and PHASE[N−1] may also change the phases of blocks in thetime domain or in the time-frequency domain to obtain a symbolarrangement. Although the above examples discuss a phase changing methodwith a period (cycle) of N, the same effects are obtainable using Nphase changing values (or phase changing sets) at random. That is, the Nphase changing values (or phase changing sets) need not always haveregular periodicity. As long as the above-described conditions aresatisfied, great quality data reception improvements are realizable forthe reception device.

Furthermore, given the existence of modes for spatial multiplexing MIMOmethods, MIMO methods using a fixed precoding matrix, space-time blockcoding methods, single-stream transmission, and methods using a regularchange of phase, the transmission device (broadcaster, base station) mayselect any one of these transmission methods.

As described in Non-Patent Literature 3, spatial multiplexing MIMOmethods involve transmitting signals s1 and s2, which are mapped using aselected modulation scheme, on each of two different antennas. MIMOmethods using a fixed precoding matrix involve performing precoding only(with no change in phase). Further, space-time block coding methods aredescribed in Non-Patent Literature 9, 16, and 17. Single-streamtransmission methods involve transmitting signal s1, mapped with aselected modulation scheme, from an antenna after performingpredetermined processing.

Schemes using multi-carrier transmission such as OFDM involve a firstcarrier group made up of a plurality of carriers and a second carriergroup made up of a plurality of carriers different from the firstcarrier group, and so on, such that multi-carrier transmission isrealized with a plurality of carrier groups. For each carrier group, anyof spatial multiplexing MIMO methods, MIMO methods using a fixedprecoding matrix, space-time block coding methods, single-streamtransmission, and methods using a regular change of phase may be used.In particular, methods using a regular change of phase on a selected(sub-)carrier group are preferably used to realize the above.

Although the present description describes the present Embodiment as atransmission device applying precoding, baseband switching, and changein phase, all of these may be variously combined. In particular, thephase changer discussed for the present Embodiment may be freelycombined with the change in phase discussed in all other Embodiments.

Embodiment D2

The present Embodiment describes a phase change initialization methodfor the regular change of phase described throughout the presentdescription. This initialization method is applicable to thetransmission device from FIG. 4 when using a multi-carrier method suchas OFDM, and to the transmission devices of FIGS. 67 and 70 when using asingle encoder and distributor, similar to FIG. 4.

The following is also applicable to a method of regularly changing thephase when encoding is performed using block codes as described inNon-Patent Literature 12 through 15, such as QC LDPC Codes (not onlyQC-LDPC but also LDPC codes may be used), concatenated LDPC and BCHcodes, Turbo codes or Duo-Binary Turbo codes using tail-biting, and soon.

The following example considers a case where two streams s1 and s2 aretransmitted. When encoding has been performed using block codes andcontrol information and the like is not necessary, the number of bitsmaking up each coded block matches the number of bits making up eachblock code (control information and so on described below may yet beincluded). When encoding has been performed using block codes or thelike and control information or the like (e.g., CRC transmissionparameters) is required, then the number of bits making up each codedblock is the sum of the number of bits making up the block codes and thenumber of bits making up the information.

FIG. 34 illustrates the varying numbers of symbols and slots needed ineach coded block when block codes are used. FIG. 34 illustrates thevarying numbers of symbols and slots needed in each coded block whenblock codes are used when, for example, two streams s1 and s2 aretransmitted as indicated by the above-described transmission device, andthe transmission device has only one encoder. (Here, the transmissionmethod may be any single-carrier method or multi-carrier method such asOFDM.)

As shown in FIG. 34, when block codes are used, there are 6000 bitsmaking up a single coded block. In order to transmit these 6000 bits,the number of required symbols depends on the modulation scheme, being3000 for QPSK, 1500 for 16-QAM, and 1000 for 64-QAM.

Then, given that the above-described transmission device transmits twostreams simultaneously, 1500 of the aforementioned 3000 symbols neededwhen the modulation scheme is QPSK are assigned to s1 and the other 1500symbols are assigned to s2. As such, 1500 slots for transmitting the1500 symbols (hereinafter, slots) are required for each of s1 and s2.

By the same reasoning, when the modulation scheme is 16-QAM, 750 slotsare needed to transmit all of the bits making up each coded block, andwhen the modulation scheme is 64-QAM, 500 slots are needed to transmitall of the bits making up each coded block.

The following describes a transmission device transmitting modulatedsignals having a frame configuration illustrated by FIGS. 71A and 71B.FIG. 71A illustrates a frame configuration for modulated signal z1′ orz1 (transmitted by antenna 312A) in the time and frequency domains.Similarly, FIG. 71B illustrates a frame configuration for modulatedsignal z2 (transmitted by antenna 312B) in the time and frequencydomains. Here, the frequency (band) used by modulated signal z1′ or z1and the frequency (band) used for modulated signal z2 are identical,carrying modulated signals z1′ or z1 and z2 at the same time.

As shown in FIG. 71A, the transmission device transmits a preamble(control symbol) during interval A. The preamble is a symboltransmitting control information for another party. In particular, thispreamble includes information on the modulation scheme used to transmita first and a second coded block. The transmission device transmits thefirst coded block during interval B. The transmission device thentransmits the second coded block during interval C.

Further, the transmission device transmits a preamble (control symbol)during interval D. The preamble is a symbol transmitting controlinformation for another party. In particular, this preamble includesinformation on the modulation scheme used to transmit a third or fourthcoded block and so on. The transmission device transmits the third codedblock during interval E. The transmission device then transmits thefourth coded block during interval D.

Also, as shown in FIG. 71B, the transmission device transmits a preamble(control symbol) during interval A. The preamble is a symboltransmitting control information for another party. In particular, thispreamble includes information on the modulation scheme used to transmita first and a second coded block. The transmission device transmits thefirst coded block during interval B. The transmission device thentransmits the second coded block during interval C.

Further, the transmission device transmits a preamble (control symbol)during interval D. The preamble is a symbol transmitting controlinformation for another party. In particular, this preamble includesinformation on the modulation scheme used to transmit a third or fourthcoded block and so on. The transmission device transmits the third codedblock during interval E. The transmission device then transmits thefourth coded block during interval D.

FIG. 72 indicates the number of slots used when transmitting the codedblocks from FIG. 34, specifically using 16-QAM as the modulation schemefor the first coded block. Here, 750 slots are needed to transmit thefirst coded block.

Similarly, FIG. 72 also indicates the number of slots used to transmitthe second coded block, using QPSK as the modulation scheme therefor.Here, 1500 slots are needed to transmit the second coded block.

FIG. 73 indicates the slots used when transmitting the coded blocks fromFIG. 34, specifically using QPSK as the modulation scheme for the thirdcoded block. Here, 1500 slots are needed to transmit the coded block.

As explained throughout this description, modulated signal z1, i.e., themodulated signal transmitted by antenna 312A, does not undergo a changein phase, while modulated signal z2, i.e., the modulated signaltransmitted by antenna 312B, does undergo a change in phase. Thefollowing phase changing method is used for FIGS. 72 and 73.

Before the change in phase can occur, seven different phase changingvalues must prepared. The seven phase changing values are labelled #0,#1, #2, #3, #4, #5, and #6. The change in phase is regular and periodic.In other words, the phase changing values are applied regularly andperiodically, such that the order is #0, #1, #2, #3, #4, #5, #6, #0, #1,#2, #3, #4, #5, #6, #0, #1, #2, #3, #4, #5, #6 and so on.

As shown in FIG. 72, given that 750 slots are needed for the first codedblock, phase changing value #0 is used initially, such that #0, #1, #2,#3, #4, #5, #6, #0, #1, #2 . . . #3, #4, #5, #6 are used in succession,with the 750th slot using #0 at the final position.

The change in phase is then applied to each slot for the second codedblock. The present description assumes multi-cast transmission andbroadcasting applications. As such, a receiving terminal may have noneed for the first coded block and extract only the second coded block.In such circumstances, given that the final slot used for the firstcoded block uses phase changing value #0, the initial phase changingvalue used for the second coded block is #1. As such, the followingmethods are conceivable:

(a): The aforementioned terminal monitors the transmission of the firstcoded block, i.e., monitors the pattern of the phase changing valuesthrough the final slot used to transmit the first coded block, and thenestimates the phase changing value used for the initial slot of thesecond coded block;

(b): (a) does not occur, and the transmission device transmitsinformation on the phase changing values in use at the initial slot ofthe second coded block.

Scheme (a) leads to greater energy consumption by the terminal due tothe need to monitor the transmission of the first coded block. However,scheme (b) leads to reduced data transmission efficiency.

Accordingly, there is a need to improve the phase changing valueallocation described above. Consider a method in which the phasechanging value used to transmit the initial slot of each coded block isfixed. Thus, as indicated in FIG. 72, the phase changing value used totransmit the initial slot of the second coded block and the phasechanging value used to transmit the initial slot of the first codedblock are identical, being #0.

Similarly, as indicated in FIG. 73, the phase changing value used totransmit the initial slot of the third coded block is not #3, but isinstead identical to the phase changing value used to transmit theinitial slot of the first and second coded blocks, being #0.

As such, the problems accompanying both methods (a) and (b) describedabove can be constrained while retaining the effects thereof.

In the present Embodiment, the method used to initialize the phasechanging value for each coded block, i.e., the phase changing value usedfor the initial slot of each coded block, is fixed so as to be #0.However, other methods may also be used for single-frame units. Forexample, the phase changing value used for the initial slot of a symboltransmitting information after the preamble or control symbol has beentransmitted may be fixed at #0.

Embodiment D3

The above-described Embodiments discuss a weighting unit using aprecoding matrix expressed in complex numbers for precoding. However,the precoding matrix may also be expressed in real numbers.

That is, suppose that two baseband signals s1(i) and s2(i) (where i istime or frequency) have been mapped (using a modulation scheme), andprecoded to obtained precoded baseband signals z1(i) and z2(i). As such,mapped baseband signal s1(i) has an in-phase component of I_(s1)(i) anda quadrature component of Q_(s1)(i), and mapped baseband signal s2(i)has an in-phase component of I_(s2)(i) and a quadrature component ofQ_(s2)(i), while precoded baseband signal z1(i) has an in-phasecomponent of Iz1(i) and a quadrature component of Q_(z1)(i), andprecoded baseband signal z2(i) has an in-phase component of I_(z2)(i)and a quadrature component of Q_(z2)(i), which gives the followingprecoding matrix H_(r) when all values are real numbers.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 76} \rbrack & \; \\{\begin{pmatrix}{I_{z\; 1}(i)} \\{Q_{z\; 1}(i)} \\{I_{z\; 2}(i)} \\{Q_{z\; 2}(i)}\end{pmatrix} = {H_{r}\begin{pmatrix}{I_{s\; 1}(i)} \\{Q_{s\; 1}(i)} \\{I_{s\; 2}(i)} \\{Q_{s\; 2}(i)}\end{pmatrix}}} & ( {{formula}\mspace{14mu} 76} )\end{matrix}$

Precoding matrix H_(r) may also be expressed as follows, where allvalues are real numbers.

$\begin{matrix}\lbrack {{Math}.\mspace{11mu} 77} \rbrack & \; \\{H_{r} = \begin{pmatrix}a_{11} & a_{12} & a_{13} & a_{14} \\a_{21} & a_{22} & a_{23} & a_{24} \\a_{31} & a_{32} & a_{33} & a_{34} \\a_{41} & a_{42} & a_{43} & a_{44}\end{pmatrix}} & ( {{formula}\mspace{14mu} 77} )\end{matrix}$

where a₁₁, a₁₂, a₁₃, a₁₄, a₂₁, a₂₂, a₂₃, a₂₄, a₃₁, a₃₂, a₃₃, a₃₄, a₄₁,a₄₂, a₄₃, and a₄₄ are real numbers. However, none of the following mayhold: {a₁₁=0, a₁₂=0, a₁₃=0, and a₁₄=0}, {a₂₁=0, a₂₂=0, a₂₃=0, anda₂₄=0}, {a₃₁=0, a₃₂=0, a₃₃=0, and a₃₄=0}, and {a₄₁=0, a₄₂=0, a₄₃=0, anda₄₄=0}. Also, none of the following may hold: {a₁₁=0, a₂₁=0, a₃₁=0, anda₄₁=0}, {a₁₂=0, a₂₂=0, a₃₂=0, and a₄₂=0}, {a₁₃=0, a₂₃=0, a₃₃=0, anda₄₃=0}, and {a₁₄=0, a₂₄=0, a₃₄=0, and a₄₄=0}.

Embodiment E1

The present Embodiment describes a transmission scheme as an applicationof the change in phase to precoded signals (or precoded signals havingswitched basebands) for a broadcasting system using the DVB-T2 (DigitalVideo Broadcasting for a second generation digital terrestrialtelevision broadcasting system) standard. First, the configuration of aframe in a broadcasting system using the DVB-T2 standard is described.

FIG. 74 illustrates the overall frame configuration of a signaltransmitted by a broadcaster using the DVB-T2 standard. Given thatDVB-T2 uses an OFDM method, the frame is configured in thetime-frequency domain. Thus, FIG. 74 illustrates frame configuration inthe time-frequency domain. The frame includes P1 signalling data (7401),L1 pre-signalling data (7402), L1 post-signalling data (7403), a commonPLP (Physical Layer Pipe) (7404), and PLPs #1 through #N (7405_1 through7405_N). (Here, L1 pre-signalling data (7402) and L1 post-signallingdata (7403) are termed P2 symbols.) As such, the P1 signalling data(7401), L1 pre-signalling data (7402), L1 post-signalling data (7403), acommon PLP (Physical Layer Pipe) (7404), and PLPs #1 through #N (7405_1through 7405_N) form a frame, which is termed a T2 frame, thusconstituting a frame configuration unit.

The P1 signalling data (7401) is a symbol used by the reception devicefor signal detection and frequency synchronization (including frequencyoffset estimation), that simultaneously serves to transmit informationsuch as the FFT size and whether the modulated signal is transmitted bya SISO or MISO method. (With SISO methods, only one modulated signal istransmitted, while with MISO methods, a plurality of modulated signalsare transmitted. In addition, the space-time blocks described inNon-Patent Literature 9, 16, and 17 may be used.)

The L1 pre-signalling data (7402) is used to transmit informationregarding the methods used to transmit the frame, concerning the guardinterval, the signal processing method information used to reduce thePAPR (Peak-to-Average Power Ratio), the modulation scheme used totransmit the L1 post-signalling data, the FEC method, the coding ratethereof, the length and size of the L1 post-signalling data, them thepayload pattern, the cell(frequency region)-specific numbers, andwhether normal mode or extended mode is in use (where normal mode andextended mode differ in terms of sub-carrier numbers used to transmitdata).

The L1 post-signalling data (7403) is used to transmit such informationas the number of PLPs, the frequency region in use, the PLP-specificnumbers, the modulation scheme used to transmit the PLPs, the FECmethod, the coding rate thereof, the number of blocks transmitted byeach PLP, and so on.

The common PLP (7404) and the PLPs #1 through #N (7405_1 through 7405_N)are areas used for data transmission.

The frame configuration from FIG. 74 illustrates the P1 signalling data(7401), L1 pre-signalling data (7402), L1 post-signalling data (7403),the common PLP (Physical Layer Pipe) (7404), and the PLPs #1 through #N(7405_1 through 7405_N) divided with respect to the time domain fortransmission. However, two or more of these signals may occursimultaneously. FIG. 75 illustrates such a case. As shown, the L1pre-signalling data, L1 post-signalling data, and common PLP occur atthe same timestamp, while PLP#1 and PLP#2 occur simultaneously atanother timestamp. That is, each signal may coexist at the same pointwith respect to the time or frequency domain within the frameconfiguration.

FIG. 76 illustrates a sample configuration of a transmission device(e.g., a broadcaster) applying a transmission method in which a changein phase is performed on precoded (or precoded and switched) signalsconforming to the DVB-T2 standard.

A PLP signal generator 7602 takes PLP transmit data 7601 (data for thePLPs) and a control signal 7609 as input, performs error-correctingcoding according to the error-correcting code information for the PLPsincluded in the control signal 7609 and performs mapping according tothe modulation scheme similarly included in the control signal 7609, andthen outputs a PLP (quadrature) baseband signal 7603.

A P2 symbol signal generator 7605 takes P2 symbol transmit data 7604 andthe control signal 7609 as input, performs error-correcting codingaccording to the error-correcting code information for the P2 symbolincluded in the control signal 7609 and performs mapping according tothe modulation scheme similarly included in the control signal 7609, andthen outputs a P2 symbol (quadrature) baseband signal 7606.

A control signal generator 7608 takes P1 symbol transmit data 7607 andthe P2 symbol transmit data 7604 as input and outputs the control signal7609 for the group of symbols from FIG. 74 (the P1 signalling data(7401), the L1 pre-signalling data (7402), the L1 post-signalling data(7403), the common PLP (7404), and PLPs #1 through #N (7405_1 through7405_N)). The control signal 7609 is made up of transmission methodinformation (such as the error-correcting codes and coding ratetherefor, the modulation scheme, the block length, the frameconfiguration, the selected transmission method in which the precodingmatrix is regularly changed, the pilot symbol insertion method, IFFT/FFTinformation, the PAPR reduction method, and the guard interval insertionmethod) for the symbol group.

A frame configurator 7610 takes a PLP baseband signal 7603, the P2symbol baseband signal 7606, and the control signal 7609 as input,performs reordering with respect to the time and frequency domainsaccording to the frame configuration information included in the controlsignal, and accordingly outputs (quadrature) baseband signal 7611_1 forstream 1 (a mapped signal, i.e., a baseband signal on which themodulation scheme has been used) and (quadrature) baseband signal 7611_2for stream 2 (also a mapped signal, i.e., a baseband signal on which themodulation scheme has been used).

A signal processor 7612 takes the baseband signal for stream 1 7611_1,the baseband signal for stream 2 7611_2, and the control signal 7609 asinput, and then outputs modulated signals 1 (7613_1) and 2 (7613_2),processed according to the transmission method included in the controlsignal 7609.

Here, the characteristic feature is that when the transmission methodfor performing the change of phase on precoded (or precoded andswitched) signals is selected, the signal processor performs the changein phase on the precoded (or precoded and switched) signals as indicatedin FIGS. 6, 25 through 29, and 69. The signals so processed are outputas processed modulated signal 1 (7613_1) and processed modulated signal2 (7613_2).

A pilot inserter 7614_1 takes processed modulated signal 1 (7613_1) andcontrol signal 7609 as input, inserts pilot symbols into processedmodulated signal 1 (7613_1) according to the pilot symbol insertionmethod information included in the control signal 7609, and outputs apost-pilot symbol insertion modulated signal 7615_1.

Another pilot inserter 7614_2 takes processed modulated signal 2(7613_2) and control signal 7609 as input, inserts pilot symbols intoprocessed modulated signal 2 (7613_2) according to the pilot symbolinsertion method information included in the control signal 7609, andoutputs a post-pilot symbol insertion modulated signal 7615_2.

An IFFT unit 7616_1 takes post-pilot symbol insertion modulated signal7615_1 and the control signal 7609 as input, applies an IFFT accordingto the IFFT method information included in the control signal 7609, andoutputs post-IFFT signal 7617_1.

Another IFFT unit 7616_2 takes post-pilot symbol insertion modulatedsignal 7615_2 and the control signal 7609 as input, applies an IFFTaccording to the IFFT method information included in the control signal7609, and outputs post-IFFT signal 7617_2.

PAPR reducer 7618_1 takes post-IFFT signal 7617_1 and control signal7609 as input, applies PAPR-reducing processing to post-IFFT signal7617_1 according to the PAPR reduction information included in thecontrol signal 7609, and outputs post-PAPR reduction signal 7619_1.

PAPR reducer 7618_2 takes post-IFFT signal 7617_2 and control signal7609 as input, applies PAPR-reducing processing to post-IFFT signal7617_2 according to the PAPR reduction information included in thecontrol signal 7609, and outputs post-PAPR reduction signal 7619_2.

Guard interval inserter 7620_1 takes post-PAPR reduction signal 7619_1and the control signal 7609 as input, inserts guard intervals intopost-PAPR reduction 7619_1 according to the guard interval insertionmethod information included in the control signal 7609, and outputspost-guard interval insertion signal 7621_1.

Guard interval inserter 7620_2 takes post-PAPR reduction signal 7619_2and the control signal 7609 as input, inserts guard intervals intopost-PAPR reduction 7619_2 according to the guard interval insertionmethod information included in the control signal 7609, and outputspost-guard interval insertion signal 7621_2.

A P1 symbol inserter 7622 takes the P1 symbol transmit data 7607 and thepost-guard interval insertion signals 7621_1 and 7621_2 as input,generates P1 symbol signals from the P1 symbol transmit data 7607, addsthe P1 symbols to the respective post-guard interval insertion signals7621_1 and 7621_2, and outputs post-P1 symbol addition signals 7623_1and 7623_2. The P1 symbol signals may be added to one or both ofpost-guard interval insertion signals 7621_1 and 7621_2. In the formercase, the signal to which nothing is added has zero signals as thebaseband signal in the interval to which the symbols are added to theother signal.

Wireless processor 7624_1 takes post-P1 symbol addition signal 7623_1 asinput, performs processing such as frequency conversion andamplification thereon, and outputs transmit signal 7625_1. Transmitsignal 7625_1 is then output as radio waves by antenna 7626_1.

Wireless processor 7624_2 takes post-P1 symbol addition signal 7623_2 asinput, performs processing such as frequency conversion andamplification thereon, and outputs transmit signal 7625_2. Transmitsignal 7625_2 is then output as radio waves by antenna 7626_2.

FIG. 77 illustrates a sample frame configuration in the time-frequencydomain where a plurality of PLPs are transmitted after the P1 symbol, P2symbol, and Common PLP have been transmitted. As shown, with respect tothe frequency domain, stream 1 (a mapped signal, i.e., a baseband signalon which the modulation scheme has been used) uses sub-carriers #1through #M, as does stream 2 (also a mapped signal, i.e., a basebandsignal on which the modulation scheme has been used). Accordingly, whenboth s1 and s2 have a symbol on the same sub-carrier at the sametimestamp, a symbol from each of the two streams is present at a singlefrequency. As explained in other Embodiments, when using a transmissionmethod that involves performing a change of phase on precoded (orprecoded and switched) signals, the change in phase may be performed inaddition to weighting using the precoding matrix (and, where applicable,after switching the baseband signal). Accordingly, signals z1 and z2 areobtained. The signals z1 and z2 are each output by a different antenna.

As shown in FIG. 77, interval 1 is used to transmit symbol group 7701 ofPLP#1 using stream s1 and stream s2. Data are transmitted using aspatial multiplexing MIMO system as illustrated by FIG. 23, or by usinga MIMO system with a fixed precoding matrix (where no change in phaseperformed).

Interval 2 is used to transmit symbol group 7702 of PLP#2 using streams1. Data are transmitted using one modulated signal.

Interval 3 is used to transmit symbol group 7703 of PLP#3 using streams1 and stream s2. Data are transmitted using a transmission method inwhich a change in phase is performed on precoded (or precoded andswitched) signals.

Interval 4 is used to transmit symbol group 7704 using stream s1 andstream s2. Data are transmitted using the time-space block codesdescribed in Non-Patent Literature 9, 16, and 17.

When a broadcaster transmits PLPs as illustrated by FIG. 77, thereception device from FIG. 77 receiving the transmit signals needs toknow the transmission method of each PLP. Accordingly, as describedabove, the L1 post-signalling data (7403 from FIG. 74), being the P2symbol, should transmit the transmission scheme for each PLP. Thefollowing describes an example of a configuration method for P1 and P2symbols in such circumstances.

Table 2 lists specific examples of control information carried by the P1symbol.

TABLE 2 S1 (3-bit) Control Information 000 T2_SISO (transmission of onemodulated signal in the DVB-T2 standard) 001 T2_MISO (transmission usingtime-space block codes in the DVB-T2 standard) 010 NOT_T2 (using astandard other than DVB-T2)

In the DVB-T2 standard, S1 control information (three bits of data) isused by the reception device to determine whether or not DVB-T2 is beingused, and in the affirmative case, to determine the transmission method.

As indicated in Table 2, above, the 3-bit S1 data are set to 000 toindicate that the modulated signals being transmitted conform totransmission of one modulated signal in the DVB-T2 standard.

Alternatively, the 3-bit S1 data are set to 001 to indicate that themodulated signals being transmitted conform to the use of time-spaceblock codes in the DVB-T2 standard.

In DVB-T2, 010 through 111 are reserved for future use. In order toapply the present invention while maintaining compatibility with DVB-T2,the 3-bit S1 data should be set to 010, for example (anything other than000 and 001 may be used), and should indicate that a standard other thanDVB-T2 is being used for the modulated signals. Thus, the receptiondevice or terminal is able to determine that the broadcaster istransmitting using modulated signals conforming to a standard other thanDVB-T2 by detecting that the data read 010.

The following describes an example of a configuration method for a P2symbol used when the modulated signals transmitted by the broadcasterconform to a standard other than DVB-T2. In the first example, a schemeof using the P2 symbol within the DVB-T2 standard.

Table 3 lists a first example of control information transmitted by theL1 post-signalling data in the P2 symbol.

TABLE 3 PLP_MODE (2-bits) Control Information 00 SISO/MIMO 01 MISO/MIMO(space-time block codes) 10 MIMO (performing a change of phase onprecoded signals (or precoded signals having switched basebands)) 11MIMO (using a fixed precoding matrix, or using spatial multiplexing)

The above-given tables use the following abbreviations.

SISO: Single-Input Single-Output (one modulated signal transmitted andreceived by one antenna)SIMO: Single-Input Multiple-Output (one modulated signal transmitted andreceived by multiple antennas)MISO: Multiple-Input Single-Output (multiple modulated signalstransmitted by multiple antennas and received by a single antenna)MIMO: Multiple-Input Multiple-Output (multiple modulated signalstransmitted and received by multiple antennas)

The two-bit data listed in Table 3 are the PLP_MODE information. Asshown in FIG. 77, this information is control information for informingthe terminal of the transmission method (symbol group of PLP#1 through#4 in FIG. 77; hereinafter, symbol group). The PLP_MODE information ispresent in each PLP. That is, in FIG. 77, the PLP_MODE information forPLP#1, for PLP#2, for PLP#3, for PLP#4, and so on, is transmitted by thebroadcaster. Naturally, the terminal acknowledges the transmissionmethod used by the broadcaster for the PLPs by demodulating (or byperforming error-correcting decoding on) this information.

When the PLP_MODE is set to 00, data are transmitted by that PLP using amethod in which a single modulated signal is transmitted. When thePLP_MODE is set to 01, data are transmitted by that PLP using a methodin which multiple modulated signals are transmitted using space-timeblock codes. When the PLP_MODE is set to 10, data are transmitted bythat PLP using a method in which a change in phase is performed onprecoded (or precoded and switched) signals. When the PLP_MODE is set to11, data are transmitted by that PLP using a method in which a fixedprecoding matrix is used, or in which a spatial multiplexing MIMOsystem, is used.

When the PLP_MODE is set to any of 01 through 11, the broadcaster musttransmit the specific processing (e.g., the specific transmission methodby which the change in phase is applied to precoded (or precoded andswitched) signals, the encoding method of time-space block codes, or theconfiguration of the precoding matrix) to the terminal. The followingdescribes an alternative to Table 3, as a configuration method forcontrol information that includes the control information necessitatedby such circumstances.

Table 4 lists a second example of control information transmitted by theL1 post-signalling data in the P2 symbol, different from that of Table3.

TABLE 4 Name No. of bits Control Information PLP_MODE 0 SISO/SISO(1-bit) 1 MIMO/MIMO, using one of (i) space-time block codes; (ii)change in phase performed on precoded signals (or precoded signalshaving switched basebands); (iii) a fixed precoding matrix; and (iv)spatial multiplexing MIMO_MODE 0 change in phase on precoded signals (or(1-bit) precoded signals having switched basebands) is OFF 1 change inphase on precoded signals (or precoded signals having switchedbasebands) is ON MIMO_PATTERN#1 00 space-time block codes (2-bit) 01fixed precoding matrix #1 10 fixed precoding matrix #2 11 spatialmultiplexing MIMO_PATTERN#2 00 change in phase on precoded signals (or(2-bit) precoded signals having switched basebands), version #1 01change in phase on precoded signals (or precoded signals having switchedbasebands), version #2 10 change in phase on precoded signals (orprecoded signals having switched basebands), version #3 11 change inphase on precoded signals (or precoded signals having switchedbasebands), version #4

As indicated in Table 4, four types of control information are possible:1-bit PLP_MODE information, 1-bit MIMO_MODE information, 2-bitMIMO_PATTERN#1 information, and 2-bit MIMO_PATTERN#2 information. Asshown in FIG. 77, the terminal is notified of the transmission methodfor each PLP (namely PLP#1 through #4) by this information. The fourtypes of control information are present in each PLP. That is, in FIG.77, the PLP_MODE information, MIMO_MODE information, MIMO_PATTERN#1information, and MIMO_PATTERN#2 information for PLP#1, for PLP#2, forPLP#3, for PLP#4, and so on, is transmitted by the broadcaster.Naturally, the terminal acknowledges the transmission method used by thebroadcaster for the PLPs by demodulating (or by performingerror-correcting decoding on) this information.

When the PLP_MODE is set to 0, data are transmitted by that PLP using amethod in which a single modulated signal is transmitted. When thePLP_MODE is set to 1, data are transmitted by that PLP using a method inwhich any one of the following applies: (i) space-time block codes areused; (ii) a MIMO system is used where a change in phase is performed onprecoded (or precoded and switched) signals; (iii) a MIMO system is usedwhere a fixed precoding matrix is used; and (iv) spatial multiplexing isused.

When the PLP_MODE is set to 1, the MIMO_MODE information is valid. Whenthe MIMO_MODE information is set to 0, data are transmitted withoutusing a change in phase performed on precoded (or precoded and switched)signals. When the MIMO_MODE information is set to 1, data aretransmitted using a change in phase performed on precoded (or precodedsignals having switched basebands).

When the PLP_MODE is set to 1 and the MIMO_MODE information is set to 0,the MIMO_PATTERN#1 information is valid. When the MIMO_PATTERN#1information is set to 00, data are transmitted using space-time blockcodes. When the MIMO_PATTERN#1 information is set to 01, data aretransmitted using fixed precoding matrix #1 for weighting. When theMIMO_PATTERN#1 information is set to 10, data are transmitted usingfixed precoding matrix #2 for weighting. (Precoding matrix #1 andprecoding matrix #2 are different matrices.) When the MIMO_PATTERN#1information is set to 11, data are transmitted using spatialmultiplexing MIMO.

When the PLP_MODE is set to 1 and the MIMO_MODE information is set to 1,the MIMO_PATTERN#2 information is valid. When the MIMO_PATTERN#2information is set to 00, data are transmitted using version #1 of achange in phase on precoded (or precoded signals having switchedbasebands). When the MIMO_PATTERN#2 information is set to 01, data aretransmitted using version #2 of a change in phase on precoded (orprecoded signals having switched basebands). When the MIMO_PATTERN#2information is set to 10, data are transmitted using version #3 of achange in phase on precoded (or precoded signals having switchedbasebands). When the MIMO_PATTERN#2 information is set to 11, data aretransmitted using version #4 of a change in phase on precoded (orprecoded signals having switched basebands). Although the change inphase is performed in four different versions #1 through 4, thefollowing three approaches are possible, given two different methods #Aand #B:

Phase changes performed using method #A and performed using method #Binclude identical and different changes.A phase changing value included in method #A is not included in method#B; and Multiple phase changes used in method #A are not included inmethod #B.

The control information listed in Table 3 and Table 4, above, istransmitted by the L1 post-signalling data in the P2 symbol. However, inthe DVB-T2 standard, the amount of information transmittable as a P2symbol is limited. Accordingly, the information listed in Tables 3 and 4is added to the information transmitted by the P2 symbol in the DVB-T2standard. When this leads to exceeding the limit on informationtransmittable as the P2 symbol, then as shown in FIG. 78, a signallingPLP (7801) may be prepared in order to transmit necessary controlinformation (at least partially, i.e., transmitting the L1post-signalling data and the signalling PLP) not included in the DVB-T2specification. While FIG. 78 illustrates a frame configuration identicalto that of FIG. 74, no limitation is intended in this regard. A specifictime and specific carrier region may also be allocated in thetime-frequency domain for the signalling PLP, as in FIG. 75. That is,the signalling PLP may be freely allocated in the time-frequency domain.

As described above, selecting a transmission method that uses amulti-carrier method such as OFDM and preserves compatibility with theDVB-T2 standard, and in which the change in phase is performed onprecoded (or precoded and switched) signals has the merits of leading tobetter reception quality in the LOS environment and to greatertransmission speeds. While the present invention describes the possibletransmission methods for the carriers as being spatial multiplexingMIMO, MIMO using a fixed precoding matrix, a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals, space-time block codes, and transmission methods transmittingonly stream s1, no limitation is intended in this manner.

Also, although the description indicates that the broadcaster selectsone of the aforementioned transmission methods, these are not the onlytransmission methods available for selection. Other options include:

MIMO using a fixed precoding matrix, a transmission method performing achange of phase on precoded (or on precoded and switched) signals,space-time block codes, and transmission methods transmitting onlystream s1;MIMO using a fixed precoding matrix, a transmission method performing achange of phase on precoded (or on precoded and switched) signals, andspace-time block codes;MIMO using a fixed precoding matrix, a transmission method performing achange of phase on precoded (or on precoded and switched) signals, andtransmission methods transmitting only stream s1;A transmission method performing a change of phase on precoded (or onprecoded and switched) signals, space-time block codes, and transmissionmethods transmitting only stream s1;MIMO using a fixed precoding matrix and a transmission method performinga change of phase on precoded (or on precoded and switched) signals;A transmission method performing a change of phase on precoded (or onprecoded and switched) signals and space-time block codes;A transmission method performing a change of phase on precoded (or onprecoded and switched) signals and transmission methods transmittingonly stream s1.As such, by including a transmission method performing a change of phaseon precoded (or on precoded and switched) signals, the merits of leadingto greater data transmission speeds in the LOS environment and betterreception quality for the reception device are achieved.

Here, given that, as described above, S1 needs to be set for the P1symbol, another configuration method for the control information(regarding the transmission method for each PLP), different from that ofTable 3, is possible. For example, Table 5, below.

TABLE 5 PLP_MODE (2-bit) Control Information 00 SISO/MIMO 01 MISO/MIMO(space-time block codes) 10 MIMO (change in phase on precoded signals(or precoded signals having switched basebands)) 11 Reserved

Table 5 differs from Table 3 in that setting the PLP_MODE information to11 is reserved. As such, when the transmission method for the PLPs is asdescribed in one of the above examples, the number of bits forming thePLP_MODE information as in the examples of Tables 3 and 5 may be madegreater or smaller according to the transmission methods available forselection.

Similarly, for Table 4, when, for example, a MIMO method is used with atransmission method that does not support changing the phase of precodedsignals (or precoded signals having switched basebands), the MIMO_MODEcontrol information is not necessary. Also, when, for example, MIMOschemes using a fixed precoding matrix are not supported, then theMIMO_PATTERN#1 is not necessary. Also, when multiple precoding matricesare not necessary, 1-bit information may be used instead of 2-bitinformation. Furthermore, two or more bits may be used when a pluralityof precoding matrices are available.

The same principles apply to the MIMO_PATTERN#2 information. When thetransmission method does not require a plurality of methods ofperforming a change of phase on precoded (or precoded and switched)signals, 1-bit information may be used instead of 2-bit information.Furthermore, two or more bits may be used when a plurality of phasechanging schemes are available.

Furthermore, although the present Embodiment describes a transmissiondevice having two antennas, no limitation is intended in this regard.The control information may also be transmitted using more than twoantennas. In such circumstances, the number of bits in each type ofcontrol information may be increased as required in order to realizetransmission using four antennas. The above description controlinformation transmission in the P1 and P2 symbol also applies to suchcases.

While FIG. 77 illustrates the frame configuration for the PLP symbolgroups transmitted by the broadcaster as being divided with respect tothe time domain, the following variation is also possible.

Unlike FIG. 77, FIG. 79 illustrates an example of a method for arrangingthe symbols stream s1 and stream 2 in the time-frequency domain, afterthe P1 symbol, the P2 symbol, and the Common PLP have been transmitted.In FIG. 79, the symbols labelled #1 are symbols of the symbol group ofPLP#1 from FIG. 77. Similarly, the symbols labelled #2 are symbols ofthe symbol group of PLP#2, the symbols labelled #3 are symbols of thesymbol group of PLP#3, and the symbols labelled #4 are symbols of thesymbol group of PLP#4, all from FIG. 77. As in FIG. 77, PLP#1 is used totransmit data using a spatial multiplexing MIMO system as illustrated byFIG. 23, or by using a MIMO system with a fixed precoding matrix. PLP#2is used to transmit data using only one modulated signal. PLP#3 is usedto transmit data using a transmission method in which a change in phaseis performed on precoded (or precoded and switched) signals. PLP#4 isused to transmit data using space-time block codes.

In FIG. 79, when both s1 and s2 have a symbol on the same sub-carrier(given as carrier in FIG. 79) at the same timestamp, a symbol from eachof the two streams is present at the common frequency. As explained inother Embodiments, when using a transmission method that involvesperforming a change of phase on precoded (or precoded and switched)signals, the change in phase may be performed in addition to weightingusing the precoding matrix (and, where applicable, after switching thebaseband signal). Accordingly, signals z1 and z2 are obtained. Thesignals z1 and z2 are each output by a different antenna.

As described above, FIG. 79 differs from FIG. 77 in that the PLPs aredivided with respect to the time domain. In addition, FIG. 79 has aplurality of PLPs arranged with respect to the time and frequencydomains. That is, for example, the symbols of PLP#1 and PLP#2 are attimestamp 1, while the symbols of PLP#3 and PLP#4 are at timestamp 3. Assuch, PLP symbols having a different index (#X, where X=1, 2, and so on)may be allocated to each symbol (made up of a timestamp and asub-carrier).

Although, for the sake of simplicity, FIG. 79 lists only #1 and #2 attimestamp 1, no limitation is intended in this regard. Indices of PLPsymbols other than #1 and #2 may be at timestamp #1. Furthermore, therelationship between PLP indices and sub-carriers at timestamp 1 is notlimited to that illustrated by FIG. 79. The indices of any PLP symbolsmay be assigned to any sub-carrier. The same applies to othertimestamps, in that the indices of any PLP symbols may be assignedthereto.

Unlike FIG. 77, FIG. 80 illustrates an example of a method for arrangingthe symbols stream s1 and stream 2 in the time-frequency domain, afterthe P1 symbol, the P2 symbol, and the Common PLP have been transmitted.The characteristic feature of FIG. 80 is that, assuming that using aplurality of antennas for transmission is the basis of the PLPtransmission method, then transmission using only stream 1 is not anoption for the T2 frame.

Accordingly, in FIG. 80, PLP symbol group 8001 transmits data using aspatial multiplexing MIMO system, or a MIMO system using a fixedprecoding matrix. Also, symbol group 8002 of PLP#2 transmits data usinga transmission method performing a change of phase on precoded (or onprecoded and switched) signals. Further, symbol group 8003 of PLP#3transmits data using space-time block code. PLP symbol groups followingsymbol group 8003 of PLP#3 transmit data using one of these methods,namely using a spatial multiplexing MIMO system, or a MIMO system usinga fixed precoding matrix, using a transmission method performing achange of phase on precoded (or on precoded and switched) signals, orusing space-time block codes.

Unlike FIG. 79, FIG. 81 illustrates an example of a method for arrangingthe symbols stream s1 and stream 2 in the time-frequency domain, afterthe P1 symbol, the P2 symbol, and the Common PLP have been transmitted.In FIG. 81, the symbols labelled #1 are symbols of the symbol group ofPLP#1 from FIG. 80. Similarly, the symbols labelled #2 are symbols ofthe symbol group of PLP#2, the symbols labelled #3 are symbols of thesymbol group of PLP#3, and the symbols labelled #4 are symbols of thesymbol group of PLP#4, all from FIG. 80. As in FIG. 80, PLP#1 is used totransmit data using a spatial multiplexing MIMO system as illustrated byFIG. 23, or by using a MIMO system with a fixed precoding matrix. PLP#2is used to transmit data using a transmission method in which a changeof phase is performed on precoded (or precoded and switched) signals.PLP#3 is used to transmit data using space-time block codes.

In FIG. 81, when both s1 and s2 have a symbol on the same sub-carrier(given as carrier in FIG. 81) at the same timestamp, a symbol from eachof the two streams is present at the common frequency. As explained inother Embodiments, when using a transmission method that involvesperforming a change of phase on precoded (or precoded and switched)signals, the change in phase may be performed in addition to weightingusing the precoding matrix (and, where applicable, after switching thebaseband signal). Accordingly, signals z1 and z2 are obtained. Thesignals z1 and z2 are each output by a different antenna.

FIG. 81 differs from FIG. 80 in that the PLPs are divided with respectto the time and frequency domains. That is, for example, the symbols ofPLP#1 and of PLP#2 are both at timestamp 1. As such, PLP symbols havinga different index (#X, where X=1, 2, and so on) may be allocated to eachsymbol (made up of a timestamp and a sub-carrier).

Although, for the sake of simplicity, FIG. 81 lists only #1 and #2 attimestamp 1, no limitation is intended in this regard. Indices of PLPsymbols other than #1 and #2 may be at timestamp #1. Furthermore, therelationship between PLP indices and sub-carriers at timestamp 1 is notlimited to that illustrated by FIG. 81. The indices of any PLP symbolsmay be assigned to any sub-carrier. The same applies to othertimestamps, in that the indices of any PLP symbols may be assignedthereto. On the other hand, one timestamp may also have symbols of onlyone PLP assigned thereto, as is the case for timestamp 3. In otherwords, any assignment of PLP symbols in the time-frequency domain isallowable.

Thus, given that the T2 frame includes no PLPs using transmissionmethods transmitting only stream s1, the dynamic range of the signalsreceived by the terminal may be constrained, which is likely to lead toimproved received signal quality.

Although FIG. 81 is described using examples of selecting one oftransmitting data using a spatial multiplexing MIMO system, or a MIMOsystem using a fixed precoding matrix, transmitting data using atransmission method performing a change of phase on precoded (or onprecoded and switched) signals, and transmitting data using space-timeblock codes, the selection of transmission method is not limited assuch. Other possibilities include:

selecting one of transmitting data using a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals, transmitting data using space-time block codes, andtransmitting data using a MIMO system using a fixed precoding matrix;selecting one of transmitting data using a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals, and transmitting data using space-time block codes; andselecting one of transmitting data using a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals and transmitting data using a MIMO system using a fixedprecoding matrix.

While the above explanation is given for a T2 frame having multiplePLPs, the following describes a T2 frame having only one PLP.

FIG. 82 illustrates a sample frame configuration for stream s1 andstream s2 in the time-frequency domain where the T2 frame has only onePLP. Although FIG. 82 indicates control symbols, these are equivalent tothe above-described symbols, such as P1 and P2 symbols. In FIG. 82,interval 1 is used to transmit a first T2 frame, interval 2 is used totransmit a second T2 frame, interval 3 is used to transmit a third T2frame, and interval 4 is used to transmit a fourth T2 frame.

Furthermore, the first T2 frame in FIG. 82 transmits symbol group 8101of PLP#1-1. The selected transmission method is spatial multiplexingMIMO or MIMO using a fixed precoding matrix.

The second T2 frame transmits symbol group 8102 of PLP#2-1. Thetransmission method is transmission using a single modulated signal.

The third T2 frame transmits symbol group 8103 of PLP#3-1. Thetransmission method is transmission performing a change of phase onprecoded (or on precoded and switched) signals.

The fourth T2 frame transmits symbol group 8104 of PLP#4-1. Thetransmission method is transmission using space-time block codes.

In FIG. 82, when both s1 and s2 have a symbol on the same sub-carrier atthe same timestamp, a symbol from each of the two streams is present atthe common frequency. As explained in other Embodiments, when using atransmission method that involves performing a change of phase onprecoded signals (or precoded signals having switched basebands), thechange in phase may be performed in addition to weighting using theprecoding matrix (and, where applicable, after switching the basebandsignal). Accordingly, signals z1 and z2 are obtained. The signals z1 andz2 are each output by a different antenna.

As such, the transmission method may be set by taking the datatransmission speed and the data reception speed of the terminal intoconsideration for each PLP. This has the dual merits of allowing thedata transmission speed to be enhanced and ensuring high data receptionquality. The configuration method for the control information pertainingto the transmission method and so on for the P1 and P2 symbols (and thesignalling PLP, where applicable) may be as given by Tables 2 through 5,thus obtaining the same effects. FIG. 82 differs from FIG. 77 in that,while the frame configuration from FIG. 77 and the like includesmultiple PLPs in a single T2 frame, thus necessitating controlinformation pertaining to the transmission method and so on of each PLP,the frame configuration of FIG. 82 includes only one PLP per T2 frame.As such, the only control information needed is for the transmissioninformation and so on pertaining the one PLP.

Although the above description discusses methods of transmittinginformation pertaining to the transmission method of PLPs using P1 andP2 symbols (and the signalling PLP, where applicable), the followingdescribes a method of transmitting information pertaining to thetransmission method of PLPs without using the P2 symbol.

FIG. 83 illustrates a frame configuration in the time-frequency domainapplicable when a terminal receiving data transmitted by a broadcasteris not compatible with the DVB-T2 standard. In FIG. 83, componentsoperating in the manner described for FIG. 74 use identical referencenumbers. The frame of FIG. 83 includes P1 signalling data (7401), firstsignalling data (8301), second signalling data (8302), a common PLP(7404), and PLPs #1 through #N (7405_1 through 7405_N). As such, the P1signalling data (7401), the first signalling data (8301), the secondsignalling data (8302), the common PLP (7404), and the PLPs #1 through#N (7405_1 through 7405_N) form a frame, thus constituting a frame unit.

The P1 signalling data (7401) are a symbol used for signal reception bythe reception device and for frequency synchronization (includingfrequency offset estimation). In addition, these data transmitidentification regarding whether or not the frame conforms to the DVB-T2standard, e.g., using the S1 data as indicated in Table 2 for thispurpose.

The first signalling data (8301) are used to transmit informationregarding the methods used to transmit the frame, concerning the guardinterval, the signal processing method information used to reduce thePAPR, the modulation scheme used to transmit the L1 post-signallingdata, the FEC method, the coding rate thereof, the length and size ofthe L1 post-signalling data, them the payload pattern, thecell(frequency region)-specific numbers, and whether normal mode orextended mode is in use, and other such information. Here, the firstsignalling data (8301) need not necessarily be data conforming to theDVB-T2 standard.

The second signalling data (8302) is used to transmit such informationas the number of PLPs, the frequency region in use, the PLP-specificnumbers, the modulation scheme used to transmit the PLPs, the FECmethod, the coding rate thereof, the number of blocks transmitted byeach PLP, and so on.

The frame configuration from FIG. 83 illustrates the first signallingdata (8301), the second signalling data (8302), the L1 post-signallingdata (7403), the common PLP (7404), and the PLPs #1 through #N (7405_1through 7405_N) divided with respect to the time domain fortransmission. However, two or more of these signals may occursimultaneously. FIG. 84 illustrates such a case. As shown in FIG. 84,the first signalling data, the second signalling data, and the commonPLP share a common timestamp, while PLP#1 and PLP#2 share a differentcommon timestamp. That is, each signal may coexist at the same pointwith respect to the time or frequency domain within the frameconfiguration.

FIG. 85 illustrates a sample configuration of a transmission device(e.g., a broadcaster) applying a transmission method in which a changein phase is performed on precoded (or precoded and switched) signals asexplained thus far, but conforming to a standard other than the DVB-T2standard. In FIG. 85, components operating in the manner described forFIG. 76 use identical reference numbers and invoke the abovedescriptions.

A control signal generator 7608 takes first and second signalling data8501 and P1 symbol transmit data 7607 as input, and outputs the controlsignal 7609 (made up of such information as the error-correcting codesand coding rate therefor, the modulation scheme, the block length, theframe configuration, the selected transmission method in which theprecoding matrix is regularly changed, the pilot symbol insertionmethod, IFFT/FFT information, the PAPR reduction method, and the guardinterval insertion method) for the transmission method of each symbolgroup of FIG. 83.

A control symbol signal generator 8502 takes the first and secondsignalling data transmit data 8501 and the control signal 7609 as input,performs error-correcting coding according to the error-correcting codeinformation for the first and second signalling data included in thecontrol signal 7609 and performs mapping according to the modulationscheme similarly included in the control signal 7609, and then outputs afirst and second signalling data (quadrature) baseband signal 8503.

In FIG. 85, the frame configurator 7610 takes the baseband signal 8503generated by the control symbol signal generator 8502 as input, ratherthan the baseband signal 7606 generated by the P2 symbol signalgenerator 7605 from FIG. 76.

The following describes, with reference to FIG. 77, a transmissionmethod for control information (information transmitted by the P1 symboland by the first and second signalling data) and for the frameconfiguration of the transmit signal for a broadcaster (base station)applying a transmission method in which a change in phase is performedon precoded (or on precoded and switched) signals in a system notconforming to the DVB-T2 standard.

FIG. 77 illustrates a sample frame configuration in the time-frequencydomain where a plurality of PLPs are transmitted after the first andsecond signalling data and the Common PLP have been transmitted. In FIG.77, stream s1 uses sub-carrier #1 through sub-carrier #M in thefrequency domain. Similarly, stream s2 also uses sub-carrier #1 throughsub-carrier #M in the frequency domain. Accordingly, when both s1 and s2have a symbol on the same sub-carrier at the same timestamp, a symbolfrom each of the two streams is present at a single frequency. Asexplained in other Embodiments, when using a transmission method thatinvolves performing a change of phase on precoded (or precoded andswitched) signals, the change in phase may be performed in addition toweighting using the precoding matrix (and, where applicable, afterswitching the baseband signal). Accordingly, signals z1 and z2 areobtained. The signals z1 and z2 are each output by a different antenna.

As shown in FIG. 77, interval 1 is used to transmit symbol group 7701 ofPLP#1 using stream s1 and stream s2. Data are transmitted using aspatial multiplexing MIMO system as illustrated by FIG. 23, or by usinga MIMO system with a fixed precoding matrix.

Interval 2 is used to transmit symbol group 7702 of PLP#2 using streams1. Data are transmitted using one modulated signal.

Interval 3 is used to transmit symbol group 7703 of PLP#3 using streams1 and stream s2. Data are transmitted using a transmission method inwhich a change in phase is performed on precoded (or precoded andswitched) signals.

Interval 4 is used to transmit symbol group 7704 of PLP#4 using streams1 and stream s2. Data are transmitted using the time-space block codes.

When a broadcaster transmits PLPs as illustrated by FIG. 77, thereception device from FIG. 64 receiving the transmit signals needs toknow the transmission method of each PLP. Accordingly, as describedabove, the first and second signalling data are used to transmit thetransmission method for each PLP. The following describes an example ofa configuration method for the P1 symbol and for the first and secondsignalling data in such circumstances. A specific example of controlinformation carried by the P1 symbol is given in Table 2.

In the DVB-T2 standard, S1 control information (three bits of data) isused by the reception device to determine whether or not DVB-T2 is beingused, and in the affirmative case, to determine the transmission method.The 3-bit S1 data are set to 000 to indicate that the modulated signalsbeing transmitted conform to transmission of one modulated signal in theDVB-T2 standard.

Alternatively, the 3-bit S1 data are set to 001 to indicate that themodulated signals being transmitted conform to the use of time-spaceblock codes in the DVB-T2 standard.

In DVB-T2, 010 through 111 are reserved for future use. In order toapply the present invention while maintaining compatibility with DVB-T2,the 3-bit S1 data should be set to 010, for example (anything other than000 and 001 may be used), and should indicate that a standard other thanDVB-T2 is being used for the modulated signals. Thus, the receptiondevice or terminal is able to determine that the broadcaster istransmitting using modulated signals conforming to a standard other thanDVB-T2 by detecting that the data read 010.

The following describes a configuration method for the first and secondsignalling data used when the modulated signals transmitted by thebroadcaster do not conform to the DVB-T2 standard. A second example ofcontrol information for the first and second signalling data is given byTable 3.

The two-bit data listed in Table 3 are the PLP_MODE information. Asshown in FIG. 77, this information is control information for informingthe terminal of the transmission method for each PLP (PLP#1 through #4in FIG. 77). The PLP_MODE information is present in each PLP. That is,in FIG. 77, the PLP_MODE information for PLP#1, for PLP#2, for PLP#3,for PLP#4, and so on, is transmitted by the broadcaster. Naturally, theterminal acknowledges the transmission method used by the broadcasterfor the PLPs by demodulating (or by performing error-correcting decodingon) this information.

When the PLP_MODE is set to 00, data are transmitted by that PLP using amethod in which a single modulated signal is transmitted. When thePLP_MODE is set to 01, data are transmitted by that PLP using a methodin which multiple modulated signals are transmitted using space-timeblock codes. When the PLP_MODE is set to 10, data are transmitted bythat PLP using a method in which a change in phase is performed onprecoded (or precoded and switched) signals. When the PLP_MODE is set to11, data are transmitted by that PLP using a method in which a fixedprecoding matrix is used, or in which a spatial multiplexing MIMOsystem, is used.

When the PLP_MODE is set to any of 01 through 11, the broadcaster musttransmit the specific processing (e.g., the specific transmission methodby which a change in phase is applied to precoded (or precoded andswitched) signals, the encoding method of time-space block codes, or theconfiguration of the precoding matrix) to the terminal. The followingdescribes an alternative to Table 3, as a configuration method forcontrol information that includes the control information necessitatedby such circumstances.

A second example of control information for the first and secondsignalling data is given by Table 4.

As indicated in Table 4, four types of control information are possible:1-bit PLP_MODE information, 1-bit MIMO_MODE information, 2-bitMIMO_PATTERN#1 information, and 2-bit MIMO_PATTERN#2 information. Asshown in FIG. 77, the terminal is notified of the transmission methodfor each PLP (namely PLP#1 through #4) by this information. The fourtypes of control information are present in each PLP. That is, in FIG.77, the PLP_MODE information, MIMO_MODE information, MIMO_PATTERN#1information, and MIMO_PATTERN#2 information for PLP#1, for PLP#2, forPLP#3, for PLP#4, and so on, is transmitted by the broadcaster.Naturally, the terminal acknowledges the transmission method used by thebroadcaster for the PLPs by demodulating (or by performingerror-correcting decoding on) this information.

When the PLP_MODE is set to 0, data are transmitted by that PLP using amethod in which a single modulated signal is transmitted. When thePLP_MODE is set to 1, data are transmitted by that PLP using a method inwhich any one of the following applies: (i) space-time block codes areused; (ii) a MIMO system is used where a change in phase is performed onprecoded (or precoded and switched) signals; (iii) a MIMO system is usedwhere a fixed precoding matrix is used; and (iv) spatial multiplexing isused.

When the PLP_MODE is set to 1, the MIMO_MODE information is valid. Whenthe MIMO_MODE information is set to 0, data are transmitted withoutusing a change in phase performed on recoded signals (or precodedsignals having switched basebands). When the MIMO_MODE information isset to 1, data are transmitted using a change in phase performed onrecoded signals (or precoded signals having switched basebands).

When the PLP_MODE information is set to 1 and the MIMO_MODE informationis set to 0, the MIMO_PATTERN#1 information is valid. As such, when theMIMO_PATTERN#1 information is set to 00, data are transmitted usingspace-time block codes. When the MIMO_PATTERN#1 information is set to01, data are transmitted using fixed precoding matrix #1 for weighting.When the MIMO_PATTERN#1 information is set to 10, data are transmittedusing fixed precoding matrix #2 for weighting. (Precoding matrix #1 andprecoding matrix #2 are different matrices.) When the MIMO_PATTERN#1information is set to 11, data are transmitted using spatialmultiplexing MIMO.

When the PLP_MODE information is set to 1 and the MIMO_MODE informationis set to 1, the MIMO_PATTERN#2 information is valid. When theMIMO_PATTERN#2 information is set to 00, data are transmitted usingversion #1 of a change in phase on precoded (or precoded and switched)signals. When the MIMO_PATTERN#2 information is set to 01, data aretransmitted using version #2 of a change in phase on precoded (orprecoded signals having switched basebands). When the MIMO_PATTERN#2information is set to 10, data are transmitted using version #3 of achange in phase on precoded (or precoded signals having switchedbasebands). When the MIMO_PATTERN#2 information is set to 11, data aretransmitted using version #4 of a change in phase on precoded (orprecoded signals having switched basebands). Although the change inphase is performed in four different versions #1 through 4, thefollowing three approaches are possible, given two different methods #Aand #B:

Phase changes performed using method #A and performed using method #Binclude identical and different changes.Some phase changing values are included in method #A but are notincluded in method #B; andMultiple phase changes used in method #A are not included in method #B.

The control information listed in Table 3 and Table 4, above, istransmitted by the first and second signalling data. In suchcircumstances, there is no particular need to use the PLPs to transmitthe control information.

As described above, selecting a transmission method that uses amulti-carrier method such as OFDM while being identifiable as differingfrom the DVB-T2 standard, and in which a change of phase is performed onprecoded (or precoded and switched) signals has the merits of leading tobetter reception quality in the LOS environment and to greatertransmission speeds. While the present invention describes the possibletransmission methods for the carriers as being spatial multiplexingMIMO, MIMO using a fixed precoding matrix, a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals, space-time block codes, and transmission methods transmittingonly stream s1, no limitation is intended in this manner.

Also, although the description indicates that the broadcaster selectsone of the aforementioned transmission methods, these are not the onlytransmission methods available for selection. Other options include:

MIMO using a fixed precoding matrix, a transmission method performing achange of phase on precoded (or on precoded and switched) signals,space-time block codes, and transmission methods transmitting onlystream s1;MIMO using a fixed precoding matrix, a transmission method performing achange of phase on precoded (or on precoded and switched) signals, andspace-time block codes;MIMO using a fixed precoding matrix, a transmission method performing achange of phase on precoded (or on precoded and switched) signals, andtransmission methods transmitting only stream s1;A transmission method performing a change of phase on precoded (or onprecoded and switched) signals, space-time block codes, and transmissionmethods transmitting only stream s1;MIMO using a fixed precoding matrix and a transmission method performinga change of phase on precoded (or on precoded and switched) signals;A transmission method performing a change of phase on precoded (or onprecoded and switched) signals and space-time block codes; andA transmission method performing a change of phase on precoded (or onprecoded and switched) signals and transmission methods transmittingonly stream s1.As such, by including a transmission method performing a change of phaseon precoded (or on precoded and switched) signals, the merits of leadingto greater data transmission speeds in the LOS environment and betterreception quality for the reception device are achieved.

Here, given that, as described above, the 51 data is set for the P1symbol, another configuration method for the control information(regarding the transmission method for each PLP) transmitted as thefirst and second signalling data, different from that of Table 3, ispossible. For example, see Table 5, above.

Table 5 differs from Table 3 in that setting the PLP_MODE information to11 is reserved. As such, when the transmission method for the PLPs is asdescribed in one of the above examples, the number of bits forming thePLP_MODE information as in the examples of Tables 3 and 5 may be madegreater or smaller according to the transmission methods available forselection.

Similarly, for Table 4, when, for example, a MIMO method is used with atransmission method that does not support changing the phase of precoded(or precoded and switched) signals, the MIMO_MODE control information isnot necessary. Also, when, for example, MIMO schemes using a fixedprecoding matrix are not supported, then the MIMO_PATTERN#1 is notnecessary. Also, when multiple precoding matrices are not necessary,1-bit information may be used instead of 2-bit information. Furthermore,two or more bits may be used when a plurality of precoding matrices areavailable.

The same principles apply to the MIMO_PATTERN#2 information. When thetransmission schemes does not require a plurality of methods ofperforming a change of phase on precoded (or precoded and switched)signals, 1-bit information may be used instead of 2-bit information.Furthermore, two or more bits may be used when a plurality of phasechanging schemes are available.

Furthermore, although the present Embodiment describes a transmissiondevice having two antennas, no limitation is intended in this regard.The control information may also be transmitted using more than twoantennas. In such circumstances, the number of bits in each type ofcontrol information may be increased as required in order to realizetransmission using four antennas. The above description controlinformation transmission in the P1 symbol and in the first and secondsignalling data also applies to such cases.

While FIG. 77 illustrates the frame configuration for the PLP symbolgroups transmitted by the broadcaster as being divided with respect tothe time domain, the following variation is also possible.

Unlike FIG. 77, FIG. 79 illustrates an example of a method for arrangingthe symbols stream s1 and stream 2 in the time-frequency domain, afterthe P1 symbol, the first and second signalling data, and the Common PLPhave been transmitted.

In FIG. 79, the symbols labelled #1 are symbols of the symbol group ofPLP#1 from FIG. 77. Similarly, the symbols labelled #2 are symbols ofthe symbol group of PLP#2, the symbols labelled #3 are symbols of thesymbol group of PLP#3, and the symbols labelled #4 are symbols of thesymbol group of PLP#4, all from FIG. 77. As in FIG. 77, PLP#1 is used totransmit data using a spatial multiplexing MIMO system as illustrated byFIG. 23, or by using a MIMO system with a fixed precoding matrix. PLP#2is used to transmit data using only one modulated signal. PLP#3 is usedto transmit data using a transmission method in which a change in phaseis performed on precoded (or precoded and switched) signals. PLP#4 isused to transmit data using space-time block codes.

In FIG. 79, when both s1 and s2 have a symbol on the same sub-carrier atthe same timestamp, a symbol from each of the two streams is present atthe common frequency. As explained in other Embodiments, when using atransmission method that involves performing a change of phase onprecoded (or precoded and switched) signals, the change in phase may beperformed in addition to weighting using the precoding matrix (and,where applicable, after switching the baseband signal). Accordingly,signals z1 and z2 are obtained. The signals z1 and z2 are each output bya different antenna.

As described above, FIG. 79 differs from FIG. 77 in that the PLPs aredivided with respect to the time domain. In addition, FIG. 79 has aplurality of PLPs arranged with respect to the time and frequencydomains. That is, for example, the symbols of PLP#1 and PLP#2 are attimestamp 1, while the symbols of PLP#3 and PLP#4 are at timestamp 3. Assuch, PLP symbols having a different index (#X, where X=1, 2, and so on)may be allocated to each symbol (made up of a timestamp and asub-carrier).

Although, for the sake of simplicity, FIG. 79 lists only #1 and #2 attimestamp 1, no limitation is intended in this regard. Indices of PLPsymbols other than #1 and #2 may be at timestamp #1. Furthermore, therelationship between PLP indices and sub-carriers at timestamp 1 is notlimited to that illustrated by FIG. 79. The indices of any PLP symbolsmay be assigned to any sub-carrier. The same applies to othertimestamps, in that the indices of any PLP symbols may be assignedthereto.

Unlike FIG. 77, FIG. 80 illustrates an example of a method for arrangingthe symbols stream s1 and stream s2 in the time-frequency domain, afterthe P1 symbol, the first and second signalling data, and the Common PLPhave been transmitted. The characteristic feature of FIG. 80 is that,assuming that using a plurality of antennas for transmission is thebasis of the PLP transmission method, then transmission using onlystream 1 is not an option for the T2 frame.

Accordingly, in FIG. 80, PLP symbol group 8001 transmits data using aspatial multiplexing MIMO system, or a MIMO system using a fixedprecoding matrix. Also, symbol group 8002 of PLP#2 transmits data usinga transmission method performing a change of phase on precoded (or onprecoded and switched) signals. Further, symbol group 8003 of PLP#3transmits data using space-time block code. PLP symbol groups followingsymbol group 8003 of PLP#3 transmit data using one of these methods,namely using a spatial multiplexing MIMO system, or a MIMO system usinga fixed precoding matrix, using a transmission method performing achange of phase on precoded (or on precoded and switched) signals, orusing space-time block codes.

Unlike FIG. 79, FIG. 81 illustrates an example of a method for arrangingthe symbols stream s1 and stream s2 in the time-frequency domain, afterthe P1 symbol, the first and second signalling data, and the Common PLPhave been transmitted.

In FIG. 81, the symbols labelled #1 are symbols of the symbol group ofPLP#1 from FIG. 80. Similarly, the symbols labelled #2 are symbols ofthe symbol group of PLP#2, the symbols labelled #3 are symbols of thesymbol group of PLP#3, and the symbols labelled #4 are symbols of thesymbol group of PLP#4, all from FIG. 80. As in FIG. 80, PLP#1 is used totransmit data using a spatial multiplexing MIMO system as illustrated byFIG. 23, or by using a MIMO system with a fixed precoding matrix. PLP#2is used to transmit data using a transmission method in which a changeof phase is performed on precoded (or precoded and switched) signals.PLP#3 is used to transmit data using space-time block codes.

In FIG. 81, when both s1 and s2 have a symbol on the same sub-carrier atthe same timestamp, a symbol from each of the two streams is present atthe common frequency. As explained in other Embodiments, when using atransmission method that involves performing a change of phase onprecoded (or precoded and switched) signals, the change in phase may beperformed in addition to weighting using the precoding matrix (and,where applicable, after switching the baseband signal). Accordingly,signals z1 and z2 are obtained. The signals z1 and z2 are each output bya different antenna.

As described above, FIG. 81 differs from FIG. 80 in that the PLPs aredivided with respect to the time domain. In addition, FIG. 81 has aplurality of PLPs arranged with respect to the time and frequencydomains. That is, for example, the symbols of PLP#1 and of PLP#2 areboth at timestamp 1. As such, PLP symbols having a different index (#X,where X=1, 2, and so on) may be allocated to each symbol (made up of atimestamp and a sub-carrier).

Although, for the sake of simplicity, FIG. 81 lists only #1 and #2 attimestamp 1, no limitation is intended in this regard. Indices of PLPsymbols other than #1 and #2 may be at timestamp #1. Furthermore, therelationship between PLP indices and sub-carriers at timestamp 1 is notlimited to that illustrated by FIG. 81. The indices of any PLP symbolsmay be assigned to any sub-carrier. The same applies to othertimestamps, in that the indices of any PLP symbols may be assignedthereto. On the other hand, one timestamp may also have symbols of onlyone PLP assigned thereto, as is the case for timestamp 3. In otherwords, any assignment of PLP symbols in the time-frequency domain isallowable.

Thus, given that the frame unit includes no PLPs using transmissionmethods transmitting only stream s1, the dynamic range of the signalsreceived by the terminal may be constrained, which is likely to lead toimproved received signal quality

Although FIG. 81 is described using examples of selecting one oftransmitting data using a spatial multiplexing MIMO system, or a MIMOsystem using a fixed precoding matrix, transmitting data using atransmission method performing a change of phase on precoded (or onprecoded and switched) signals, and transmitting data using space-timeblock codes, the selection of transmission method is not limited assuch. Other possibilities include:

selecting one of transmitting data using a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals, transmitting data using space-time block codes, andtransmitting data using a MIMO system using a fixed precoding matrix;selecting one of transmitting data using a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals, and transmitting data using space-time block codes; andselecting one of transmitting data using a transmission methodperforming a change of phase on precoded (or on precoded and switched)signals and transmitting data using a MIMO system using a fixedprecoding matrix.

While the above explanation is given for a frame unit having multiplePLPs, the following describes a frame unit having only one PLP.

FIG. 82 illustrates a sample frame configuration for stream s1 andstream s2 in the time-frequency domain where the frame unit has only onePLP.

Although FIG. 82 indicates control symbols, these are equivalent to theabove-described P1 symbol and to the first and second signalling data.In FIG. 82, interval 1 is used to transmit a first frame unit, interval2 is used to transmit a second frame unit, interval 3 is used totransmit a third frame unit, and interval 4 is used to transmit a fourthframe unit.

Furthermore, the first frame unit in FIG. 82 transmits symbol group 8101of PLP#1-1. The transmission method is spatial multiplexing MIMO or MIMOusing a fixed precoding matrix.

The second frame unit transmits symbol group 8102 of PLP#2-1. Thetransmission method is transmission using a single modulated signal.

The third frame unit transmits symbol group 8103 of PLP#3-1. Thetransmission method is a transmission method performing a change ofphase on precoded (or on precoded and switched) signals.

The fourth frame unit transmits symbol group 8104 of PLP#4-1. Thetransmission method is transmission using space-time block codes.

In FIG. 82, when both s1 and s2 have a symbol on the same sub-carrier atthe same timestamp, a symbol from each of the two streams is present atthe common frequency. When using a transmission method that involvesperforming a change of phase on precoded (or precoded and switched)signals, the change in phase may be performed in addition to weightingusing the precoding matrix (and, where applicable, after switching thebaseband signal). Accordingly, signals z1 and z2 are obtained. Thesignals z1 and z2 are each output by a different antenna.

As such, the transmission method may be set by taking the datatransmission speed and the data reception speed of the terminal intoconsideration for each PLP. This has the dual merits of allowing thedata transmission speed to be enhanced and ensuring high data receptionquality. The configuration method for the control information pertainingto the transmission method and so on for the P1 symbol and for the firstand second signalling data may be as given by Tables 2 through 5, thusobtaining the same effects. The frame configuration of FIG. 82 differsfrom that of FIG. 77 and the like, where each frame unit has multiplePLPs, and control information pertaining to the transmission method foreach of the PLPs is required. In FIG. 82, each frame unit has only onePLP, and thus, the only control information needed is for thetransmission information and so on pertaining to that single PLP.

The present Embodiment describes a method applicable to a system using aDVB standard and in which the transmission method involves performing achange of phase on precoded (or precoded and switched) signals. Thetransmission method involving performing a change of phase on precodedsignals (or precoded signals having switched basebands) is described inthe present description. Although the present Embodiment uses “controlsymbol” as a term of art, this term has no influence on the presentinvention.

The following describes the space-time block codes discussed in thepresent description and included in the present Embodiment.

FIG. 94 illustrates the configuration of a modulated signal usingspace-time block codes. As shown, a space-time block coder (9402) takesa baseband signal based on a modulated signal as input. For example, thespace-time block coder (9402)takes symbol s1, symbol s2, and so on asinput. Then, as shown in FIG. 94, space-time block coding is performed,resulting in z1 (9403A) taking s1 as symbol #0, −s2* as symbol #1, s3 assymbol #2, −s4* as symbol #3, and so on, and z2 (9403B) taking s2 assymbol #0, s1* as symbol #1, s4 as symbol #2, s3* as symbol #3, and soon. Here, symbol #X of z1 and symbol #X of z2 are simultaneous signalson a common frequency, each broadcast from a different antenna. Thearrangement of symbols in the space-time block codes is not restrictedto the time domain. A group of symbols may also be arranged in thefrequency domain, or in the time-frequency domain, as required.Furthermore, the space-time block coding method of FIG. 94 is given asan example of space-time block codes. Other space-time block codes mayalso be applied to each Embodiment discussed in the present description.

Embodiment E2

The present Embodiment describes a reception method and a receptiondevice applicable to a communication system using the DVB-T2 standardwhen the transmission method described in Embodiment E1, which involvesperforming a change of phase on precoded (or on precoded and switched)signals, is used.

FIG. 86 illustrates a sample configuration for a reception device in aterminal, for use when the transmission device of the broadcaster fromFIG. 76 applies a transmission method involving a change in phase ofprecoded (or precoded and switched) signals. Components thereofoperating identically to those of FIG. 7 use the same reference numbersthereas.

In FIG. 86, a P1 symbol detector and decoder 8601 receives the signaltransmitted by the broadcaster and takes baseband signals 704_X and704_Y as input, thereby performing signal detection and frequencysynchronization. The P1 symbol detector and decoder 8601 simultaneouslyobtains the control information included in the P1 symbol (by performingdemodulation and error-correcting decoding thereon) and outputs the P1symbol control information 8602 so obtained.

OFDM-related processors 8600_X and 8600_Y take the P1 symbol controlinformation 8602 as input and modify the OFDM signal processing method(such as the Fourier transform) accordingly. (This is possible because,as described in Embodiment E1, the signals transmitted by thebroadcaster include transmission method information in the P1 symbol.)The OFDM-related processors 8600_X and 8600_Y then output the basebandsignals 704_X and 704_Y after performing demodulation thereon accordingto the signal processing method.

A P2 symbol demodulator 8603 (which may also apply to the signallingPLP) takes the baseband signals 704_X and 704_Y and the P1 symbolcontrol information 8602 as input, performs signal processing anddemodulation (including error-correcting decoding) in accordance withthe P1 symbol control information, and outputs P2 symbol controlinformation 8604.

A control information generator 8605 takes the P1 symbol controlinformation 8602 and the P2 symbol control information 8604 as input,bundles the control information (pertaining to reception operations),and outputs a control signal 8606. Then, as shown in FIG. 86, thecontrol signal 8606 is input to each component.

A signal processor 711 takes signals 706_1, 706_2, 708_1, 708_2, 704_X,and 704_Y, as well as control signal 8606, as input, performsdemodulation an decoding according to the information included in thecontrol signal 8606, and outputs received data 712. The informationincluded in the control signal pertains to the transmission method,modulation scheme, error-correcting coding method and coding ratethereof, error-correcting code block size, and so on used for each PLP.

When the transmission method used for the PLPs is one of spatialmultiplexing MIMO, MIMO using a fixed precoding matrix, and atransmission method performing a change of phase on precoded (or onprecoded and switched) signals, demodulation is performed by obtainingreceived (baseband) signals using the output of the channel estimators(705_1, 705_2, 707_1, and 707_2) and the relationship of the received(baseband) signals to the transmit signals. When the transmission methodinvolves performing a change of phase on precoded (or precoded andswitched) signals, demodulation is performed using the output of thechannel estimators (705_1, 705_2, 707_1, and 707_2), the received(baseband) signals, and the relationship given by Math. 48 (formula 48).

FIG. 87 illustrates a sample configuration for a reception device in aterminal, for use when the transmission device of the broadcaster fromFIG. 85 applies a transmission method involving a change in phase ofprecoded (or precoded and switched) signals. Components thereofoperating identically to those of FIGS. 7 and 86 use the same referencenumbers thereas.

The reception device from FIG. 87 differs from that of FIG. 86 in that,while the latter receives data from signals conforming to the DVB-T2standard and to other standards, the former receives data only fromsignals conforming to a standard other than DVB-T2.

In FIG. 87, a P1 symbol detector and decoder 8601 receives the signaltransmitted by the broadcaster and takes baseband signals 704_X and704_Y as input, thereby performing signal detection and frequencysynchronization. The P1 symbol detector and decoder 8601 simultaneouslyobtains the control information included in the P1 symbol (by performingdemodulation and error-correcting decoding thereon) and outputs the P1symbol control information 8602 so obtained.

OFDM-related processors 8600_X and 8600_Y take the P1 symbol controlinformation 8602 as input and modify the OFDM signal processing methodaccordingly. (This is possible because, as described in Embodiment E1,the signals transmitted by the broadcaster include transmission methodinformation in the P1 symbol.) The OFDM-related processors 8600_X and8600_Y then output the baseband signals 704_X and 704_Y after performingdemodulation thereon according to the signal processing method.

A first and second signalling data demodulator 8701 (which may alsoapply to the signalling PLP) takes the baseband signals 704_X and 704_Yand the P1 symbol control information 8602 as input, performs signalprocessing and demodulation (including error-correcting decoding) inaccordance with the P1 symbol control information, and outputs first andsecond signalling data control information 8702.

A control information generator 8605 takes the P1 symbol controlinformation 8602 and the first and second signalling data controlinformation 8702 as input, bundles the control information (pertainingto reception operations), and outputs a control signal 8606. Then, asshown in FIG. 86, the control signal 8606 is input to each component.

A signal processor 711 takes signals 706_1, 706_2, 708_1, 708_2, 704_X,and 704_Y, as well as control signal 8606, as input, performsdemodulation an decoding according to the information included in thecontrol signal 8606, and outputs received data 712. The informationincluded in the control signal pertains to the transmission method,modulation scheme, error-correcting coding method and coding ratethereof, error-correcting code block size, and so on used for each PLP.

When the transmission method used for the PLPs is one of spatialmultiplexing MIMO, MIMO using a fixed precoding matrix, and atransmission method performing a change of phase on precoded (or onprecoded and switched) signals, demodulation is performed by obtainingreceived (baseband) signals using the output of the channel estimators(705_1, 705_2, 707_1, and 707_2) and the relationship of the received(baseband) signals to the transmit signals. When the transmission methodinvolves performing a change of phase on precoded (or precoded andswitched) signals, demodulation is performed using the output of thechannel estimators (705_1, 705_2, 707_1, and 707_2), the received(baseband) signals, and the relationship given by Math. 48 (formula 48).

FIG. 88 illustrates the configuration of a reception device for aterminal compatible with the DVB-T2 standard and with standards otherthan DVB-T2. Components thereof operating identically to those of FIGS.7 and 86 use the same reference numbers thereas.

FIG. 88 differs from FIGS. 86 and 87 in that the reception device of theformer is compatible with signals conforming to the DVB-T2 standard aswell as signals conforming to other standards. As such, the receptiondevice includes a P2 symbol or first and second signalling datademodulator 8801, in order to enable demodulation.

The P2 symbol or first and second signalling data demodulator 8801 takesthe baseband signals 704_X and 704_Y, as well as the P1 symbol controlinformation 8602, as input, uses the P1 symbol control information todetermine whether the received signals conform to the DVB-T2 standard orto another standard (e.g., using Table in such a determination),performs signal processing and demodulation (including error-correctingdecoding), and outputs control information 8802, which includesinformation indicating the standard to which the received signalsconform. Otherwise, the operations are identical to those explained forFIGS. 86 and 87.

A reception device configured as described in the above Embodiment andreceiving signals transmitted by a broadcaster having the transmissiondevice described in Embodiment E1 provides higher received data qualityby applying appropriate signal processing. In particular, when receivingsignals transmitted using a transmission method that involves a changein phase applied to precoded (or precoded and switched) signals, datatransmission effectiveness as well as signal quality are both improvedin the LOS environment.

Although the present Embodiment is described as a reception devicecompatible with the transmission method described in Embodiment E1, andtherefore having two antennas, no limitation is intended in this regard.The reception device may also have three or more antennas. In suchcases, the data reception quality may be further improved by enhancingthe diversity gain. Also, the transmission device of the broadcaster mayhave three or more transmit antennas and transmit three or moremodulated signals. The same effects are achievable by accordinglyincreasing the number of antennas on the reception device of theterminal. Alternatively, the reception device may have only one antennaand apply maximum likelihood detection or approximate maximum likelihooddetection. In such circumstances, the transmission method is preferablyone that involves a change in phase of precoded (or precoded andswitched) signals.

The transmission method need not be limited to the specific methodsexplained in the present description. As long as precoding occurs and ispreceded or followed by a change in phase, the same results areobtainable for the present Embodiment.

Embodiment E3

The system of Embodiment E1, which applies, to the DVB-T2 standard, atransmission method involving a change in phase performed on precoded(or precoded and switched) signals, includes control informationindicating the pilot insertion method in the L1 pre-signallinginformation. The present Embodiment describes a method of applying atransmission method that involves a change in phase performed onprecoded signals (or precoded signals having switched basebands) whenthe pilot insertion method in the L1 pre-signalling information ischanged.

FIGS. 89A, 89B, 90A, and 90B illustrate sample frame configurationsconforming to the DVB-T2 standard in the time-frequency domain in whicha common frequency region is used in a transmission method by which aplurality of modulated signals are transmitted from a plurality ofantennas. Here, the horizontal axes represent frequency, i.e., thecarrier numbers, while the vertical axes represent time. FIGS. 89A and90A illustrate frame configurations for modulated signal z1 while FIGS.89B and 90B illustrate frame configurations for modulated signal z2,both of which are as explained in the above Embodiments. The carriernumbers are labelled f0, f1, f2, and so on, while time is labelled t1,t2, t3 and so on. Also, symbols indicated at the same carrier and timeare simultaneous symbols at a common frequency.

FIGS. 89A, 89B, 90A, and 90B illustrate examples of pilot symbolinsertion positions conforming to the DVB-T2 standard. (In DVB-T2, eightmethods of pilot insertion are possible when a plurality of antennas areused to transmit a plurality of modulated signals. Two of these arepresently illustrated.) Two types of symbols are indicated, namely pilotsymbols and data symbols. As described for other Embodiments, when thetransmission method involves performing a change of phase on precodedsignals (or precoded signals having switched basebands), or involvesprecoding using a fixed precoding matrix, then the data symbols ofmodulated signal z1 are symbols of stream s1 and stream s2 that haveundergone weighting, as are the data symbols of modulated signal z2.(However, a change in phase is also performed when the transmissionscheme involves doing so) When space-time block codes or a spatialmultiplexing MIMO system are used, the data symbols of modulated signalz1 are the symbols of either stream s1 or of stream s2, as are thesymbols of modulated signal z2. In FIGS. 89A, 89B, 90A, and 90B, thepilot symbols are labelled with an index, which is either PP1 or PP2.These represent pilot symbols using different configuration methods. Asdescribed above, eight methods of pilot insertion are possible in DVB-T2(varying in terms of the frequency at which pilot symbols are insertedin the frame), one of which is indicated by the broadcaster. FIGS. 89A,89B, 90A, and 90B illustrate two pilot insertion methods among theseeight. As described in Embodiment E1, information pertaining to thepilot insertion method selected by the broadcaster is transmitted to thereceiving terminal as the L1 pre-signalling data in the P2 symbol.

The following describes a method of applying a transmission methodinvolving a change in phase performed on precoded signals (or precodedsignals having switched basebands) complementing the pilot insertionmethod. In this example, the transmission method involves preparing tendifferent phase changing values, namely F[0], F[1], F[2], F[3], F[4],F[5], F[6], F[7], F[8], and F[9]. FIGS. 91A and 91B illustrate theallocation of these phase changing values in the time-frequency domainframe configuration of FIGS. 89A and 89B when a transmission methodinvolving a change in phase performed on precoded (or precoded andswitched) signals is applied. Similarly, FIGS. 92A and 92B illustratethe allocation of these phase changing values in the time-frequencydomain frame configuration of FIGS. 90A and 90B when a transmissionmethod involving a change in phase performed on precoded (or precodedand switched) signals is applied. For example, FIG. 91A illustrates theframe configuration of modulated signal z1 while FIG. 91B illustratesthe frame configuration of modulated signal z2. In both cases, symbol #1at f1, t1 is a symbol on which frequency modification has been performedusing phase changing value F[1]. Accordingly, in FIGS. 91A, 91B, 92A,and 92B, a symbol at carrier fx (where x=0, 1, 2, and so on), time ty(where y=1, 2, 3, and so on) is labelled #Z to indicate that frequencymodification has been performed using phase changing value F[Z] on thesymbol fx, ty.

Naturally, the insertion method (insertion interval) for thefrequency-time frame configuration of FIGS. 91A and 91B differs fromthat of FIGS. 92A and 92B. The transmission method in which a change ofphase is performed on precoded signals (or precoded signals havingswitched basebands) is not applied to the pilot symbols. Therefore,although the same transmission method involving a change in phaseperformed on the same synchronized precoded (or precoded and switched)signals (for which a different number of phase changing values may havebeen prepared), the phase changing value assigned to a single symbol ata given carrier and time in FIGS. 91A and 91B may be different in FIGS.92A and 92B. This is made clear by reference to the drawings. Forexample, the symbol at f5, t2 in FIGS. 91A and 91B is labelled #7,indicating that a change in phase has been performed thereon using phasechanging value F[7]. On the other hand, the symbol at f5, t2 in FIGS.92A and 92B is labelled #8, indicating that a change in phase has beenperformed thereon using phase changing value F[8].

Accordingly, although the broadcaster transmits control informationindicating the pilot pattern (pilot insertion method) in the L1pre-signalling information, when the transmission method selected by thebroadcaster method involves a change in phase performed on precodedsignals (or precoded signals having switched basebands), the controlinformation may additionally indicate the phase changing valueallocation method used in the selected method through the controlinformation given by Table 3 or Table 4. Thus, the reception device ofthe terminal receiving the modulated signals transmitted by thebroadcaster is able to determine the phase changing value allocationmethod by obtaining the control information indicating the pilot patternin the L1 pre-signalling data. (This presumes that the transmissionmethod selected by the broadcaster for PLP transmission from Table 3 orTable 4 is one that involves a change in phase on precoded signals (orprecoded signals having switched basebands)). Although the abovedescription uses the example of L1 pre-signalling data, theabove-described control information may also be included in the firstand second signalling data when, as described for FIG. 83, no P2 symbolsare used.

The following describes further variant examples. Table 6 lists samplephase changing patterns and corresponding modulation schemes.

TABLE 6 No. of Modulated Modulation Phase Changing Signals SchemePattern 2 #1: QPSK, #1: —, #2: QPSK #2: A 2 #1: QPSK, #1: —, #2: 16-QAM#2: B 2 #1: 16-QAM, #1: —, #2: 16-QAM #2: C . . . . . . . . .

For example, as shown in Table 6, when the modulation scheme isindicated and the phase changing values to be used in the transmissionmethod involving a change in phase performed on precoded signals (orprecoded signals having switched basebands) have been determined, theabove-described principles apply. That is, transmitting only the controlinformation pertaining to the pilot pattern, the PLP transmissionmethod, and the modulation scheme suffices to enable the receptiondevice of the terminal to estimate the phase changing value allocationmethod (in the time-frequency domain) by obtaining this controlinformation. In Table 6, the Phase Changing Method column lists a dashto indicate that no change in phase is performed, and lists #A, #B, or#C to indicate phase changing methods #A, #B, and #C. Similarly, asshown in Table 1, when the modulation scheme and the error-correctingcoding method are indicated and the phase changing values to be used inthe transmission method involving a change in phase of precoded signals(or precoded signals having switched basebands) have been determined,then transmitting only the control information pertaining to the pilotpattern, the PLP transmission method, the modulation scheme, and theerror-correcting codes in the P2 symbol suffices to enable the receptiondevice of the terminal to estimate the phase changing value allocationmethod (in the time-frequency domain) by obtaining this controlinformation.

However, unlike Table 1 and Table 6, two or more different types oftransmission scheme involving a change in phase performed on precodedsignals (or precoded signals having switched basebands) may be selected,despite the modulation scheme having been determined (For example, thetransmission schemes may have a different period (cycle), or usedifferent phase changing values). Alternatively, two or more differenttypes of transmission scheme involving a change in phase performed onprecoded signals (or precoded signals having switched basebands) may beselected, despite the modulation scheme and the error-correction schemehaving been determined. Furthermore, two or more different types oftransmission scheme involving a change in phase performed on precodedsignals (or precoded signals having switched basebands) may be selected,despite the error-correction scheme having been determined. In suchcases, as shown in Table 4, the transmission scheme involves switchingbetween phase changing values. However, information pertaining to theallocation scheme of the phase changing values (in the time-frequencydomain) may also be transmitted.

Table 7 lists control information configuration examples for informationpertaining to such allocation methods.

TABLE 7 PHASE_FRAME_ARRANGEMENT (2-bit) Control Information 00allocation scheme #1 01 allocation scheme #2 10 allocation scheme #3 11allocation scheme #4

For example, suppose that the transmission device of the broadcasterselects FIGS. 89A and 89B as the pilot pattern insertion method, andselects transmission method A, which involves a change in phase onprecoded signals (or precoded signals having switched basebands). Thus,the transmission device may select FIGS. 91A and 91B or FIGS. 93A and93B as the phase changing value allocation method (in the time-frequencydomain). For example, when the transmission device selects FIGS. 91A and91B, the PHASE_FRAME_ARRANGEMENT information of Table 7 is set to 00.When the transmission device selects FIGS. 93A and 93B, thePHASE_FRAME_ARRANGEMENT information is set to 01. As such, the receptiondevice is able to determine the phase changing value allocation method(in the time-frequency domain) by obtaining the control information ofTable 7. The control information of Table 7 is also applicable totransmission by the P2 symbol, and to transmission by the first andsecond signalling data.

As described above, a phase changing value allocation method for thetransmission method involving a change in phase performed on precoded(or precoded and switched) signals may be realized through the pilotinsertion method. In addition, by reliably transmitting such allocationmethod information to the receiving party, the reception device derivesthe dual benefits of improved data transmission efficiency and enhancedreceived signal quality.

Although the present Embodiment describes a broadcaster using twotransmit signals, the same applies to broadcasters using a transmissiondevice having three or more transmit antennas transmitting three or moresignals. The transmission method need not be limited to the specificmethods explained in the present description. As long as precodingoccurs and is preceded or followed by a change in phase, the sameresults are obtainable for the present Embodiment.

The pilot signal configuration method is not limited to the presentEmbodiment. When the transmission method involves performing a change ofphase on precoded (or precoded and switched) signals, the receptiondevice need only implement the relationship given by Math. 48 (formula48) (e.g., the reception device may know the pilot pattern signalstransmitted by the transmission device in advance). This applies to allEmbodiments discussed in the present description.

The transmission devices pertaining to the present invention, asillustrated by FIGS. 3, 4, 12, 13, 51, 52, 67, 70, 76, 85, and so ontransmit two modulated signals, namely modulated signal #1 and modulatedsignal #2, on two different transmit antennas. The average transmissionpower of the modulated signals #1 and #2 may be set freely. For example,when the two modulated signals each have a different averagetransmission power, conventional transmission power control technologyused in wireless transmission systems may be applied thereto. Therefore,the average transmission power of modulated signals #1 and #2 maydiffer. In such circumstances, transmission power control may be appliedto the baseband signals (e.g., when mapping is performed using themodulation scheme), or may be performed by a power amplifier immediatelybefore the antenna.

Embodiment F1

The schemes for regularly performing phase change on the modulatedsignal after precoding described in Embodiments 1 through 4, EmbodimentA1, Embodiments C1 through C7, Embodiments D1 through D3 and EmbodimentsE1 through E3 are applicable to any baseband signals s1 and s2 mapped inthe I-Q plane. Therefore, in Embodiments 1 through 4, Embodiment A1,Embodiments C1 through C7, Embodiments D1 through D3 and Embodiments E1through E3, the baseband signals s1 and s2 have not been described indetail. On the other hand, when the scheme for regularly performingphase change on the modulated signal after precoding is applied to thebaseband signals s1 and s2 generated from the error correction codeddata, excellent reception quality can be achieved by controlling averagepower (average value) of the baseband signals s1 and s2. In the presentembodiment, the following describes a scheme of setting the averagepower of s1 and s2 when the scheme for regularly performing phase changeon the modulated signal after precoding is applied to the basebandsignals s1 and s2 generated from the error correction coded data.

As an example, the modulation schemes for the baseband signal s1 and thebaseband signal s2 are described as QPSK and 16QAM, respectively.

Since the modulation scheme for s1 is QPSK, s1 transmits two bits persymbol. Let the two bits to be transmitted be referred to as b0 and b1.On the other hand, since the modulation scheme for s2 is 16QAM, s2transmits four bits per symbol. Let the four bits to be transmitted bereferred to as b2, b3, b4 and b5. The transmission device transmits oneslot composed of one symbol for s1 and one symbol for s2, i.e. six bitsb0, b1, b2, b3, b4 and b5 per slot.

For example, in FIG. 95 as an example of signal point layout in the I-Qplane for 16QAM, (b2, b3, b4, b5)=(0, 0, 0, 0) is mapped onto (I,Q)=(3×g, 3×g), (b2, b3, b4, b5)=(0, 0, 0, 1) is mapped onto (I, Q)=(3×g,1×g), (b2, b3, b4, b5)=(0, 0, 1, 0) is mapped onto (I, Q)=(1×g, 3×g),(b2, b3, b4, b5)=(0, 0, 1, 1) is mapped onto (I, Q)=(1×g, 1×g), (b2, b3,b4, b5)=(0, 1, 0, 0) is mapped onto (I, Q)=(3×g, −3×g), . . . , (b2, b3,b4, b5)=(1, 1, 1, 0) is mapped onto (I, Q)=(−1×g, −3×g), and (b2, b3,b4, b5)=(1, 1, 1, 1) is mapped onto (I, Q)=(−1×g, −1×g). Note that b2through b5 shown on the top right of FIG. 95 shows the bits and thearrangement of the numbers shown on the I-Q plane.

Also, in FIG. 96 as an example of signal point layout in the I-Q planefor QPSK, (b0, b1)=(0, 0) is mapped onto (I, Q)=(1×h, 1×h), (b0,b1)=(0, 1) is mapped onto (I, Q)=(1×h, −1×h), (b0, b1)=(1, 0) is mappedonto (I, Q)=(−1×h, 1×h), and (b0, b1)=(1, 1) is mapped onto (I,Q)=(−1×h, −1×h). Note that b0 and b1 shown on the top right of FIG. 96shows the bits and the arrangement of the numbers shown on the I-Qplane.

Here, assume that the average power of s1 is equal to the average powerof s2, i.e. h shown in FIG. 96 is represented by formula 78 and g shownin FIG. 95 is represented by formula 79.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 78} \rbrack & \; \\{h = \frac{z}{\sqrt{2}}} & ( {{formula}\mspace{14mu} 78} ) \\\lbrack {{Math}.\mspace{14mu} 79} \rbrack & \; \\{g = \frac{z}{\sqrt{10}}} & ( {{formula}\mspace{14mu} 79} )\end{matrix}$

FIG. 97 shows the log-likelihood ratio obtained by the reception devicein this case. FIG. 97 schematically shows absolute values of thelog-likelihood ratio for b0 through b5 described above when thereception device obtains the log-likelihood ratio. In FIG. 97, 9700 isthe absolute value of the log-likelihood ratio for b0, 9701 is theabsolute value of the log-likelihood ratio for b1, 9702 is the absolutevalue of the log-likelihood ratio for b2, 9703 is the absolute value ofthe log-likelihood ratio for b3, 9704 is the absolute value of thelog-likelihood ratio for b4, and 9705 is the absolute value of thelog-likelihood ratio for b5. In this case, as shown in FIG. 97, when theabsolute values of the log-likelihood ratio for b0 and b1 transmitted inQPSK are compared with the absolute values of the log-likelihood ratiofor b2 through b5 transmitted in 16QAM, the absolute values of thelog-likelihood ratio for b0 and b1 are higher than the absolute valuesof the log-likelihood ratio for b2 through b5. That is, reliability ofb0 and b1 in the reception device is higher than the reliability of b2through b5 in the reception device. This is because of the followingreason. When h is represented by formula 79 in FIG. 95, a minimumEuclidian distance between signal points in the I-Q plane for QPSK is asfollows.

[Math. 80]

√{square root over (2)}z  (formula 80)

On the other hand, when h is represented by formula 78 in FIG. 78, aminimum Euclidian distance between signal points in the I-Q plane for16QAM is as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 81} \rbrack & \; \\{\frac{2}{\sqrt{10}}z} & ( {{formula}\mspace{14mu} 81} )\end{matrix}$

This is the reason.

If the reception device performs error correction decoding (e.g. beliefpropagation decoding such as a sum-product decoding in a case where thecommunication system uses LDPC codes) under this situation, due to adifference in reliability that “the absolute values of thelog-likelihood ratio for b0 and b1 are higher than the absolute valuesof the log-likelihood ratio for b2 through b5”, a problem that the datareception quality degrades in the reception device by being affected bythe absolute values of the log-likelihood ratio for b2 through b5arises.

In order to overcome the problem, the difference between the absolutevalues of the log-likelihood ratio for b0 and b1 and the absolute valuesof the log-likelihood ratio for b2 through b5 should be reduced comparedwith FIG. 97, as shown in FIG. 98.

Therefore, it is considered that the average power (average value) of s1is made to be different from the average power (average value) of s2.FIGS. 99 and 100 each show an example of the structure of the signalprocessor relating to a power changer (although being referred to as thepower changer here, the power changer may be referred to as an amplitudechanger or a weight unit) and the weighting (precoding) unit. In FIG.99, elements that operate in a similar way to FIG. 3 and FIG. 6 bear thesame reference signs. Also, in FIG. 100, elements that operate in asimilar way to FIG. 3, FIG. 6 and FIG. 99 bear the same reference signs.

The following explains some examples of operations of the power changer.

Example 1

First, an example of the operation is described using FIG. 99. Let s1(t)be the (mapped) baseband signal for the modulation scheme QPSK. Themapping scheme for s1(t) is as shown in FIG. 96, and h is as representedby formula 78. Also, let s2(t) be the (mapped) baseband signal for themodulation scheme 16QAM. The mapping scheme for s2(t) is as shown inFIG. 95, and g is as represented by formula 79. Note that t is time. Inthe present embodiment, description is made taking the time domain as anexample.

The power changer (9901B) receives a (mapped) baseband signal 307B forthe modulation scheme 16QAM and a control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be u, the power changer outputs a signal (9902B) obtained by multiplyingthe (mapped) baseband signal 307B for the modulation scheme 16QAM by u.Let u be a real number, and u>1.0. Letting the precoding matrix used inthe scheme for regularly performing phase change on the modulated signalafter precoding be F and the phase changing value used for regularlyperforming phase change be y(t) (y(t) may be imaginary number having theabsolute value of 1, i.e. ej^(θ(t)), the following formula is satisfied.

$\begin{matrix}( {{formula}\mspace{14mu} 82} ) & \; \\\begin{matrix}{\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix} = {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}^{j\; 0} & 0 \\0 & {u\; ^{j\; 0}}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}1 & 0 \\0 & u\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 82} \rbrack\end{matrix}$

Therefore, a ratio of the average power for QPSK to the average powerfor 16QAM is set to 1:u². With this structure, the reception device isin a reception condition in which the absolute value of thelog-likelihood ratio shown in FIG. 98 is obtained. Therefore, datareception quality is improved in the reception device.

The following describes a case where u in the ratio of the average powerfor QPSK to the average power for 16QAM 1:u² is set as shown in thefollowing formula.

[Math. 83]

u=√{square root over (5)}  (formula 83)

In this case, the minimum Euclidian distance between signal points inthe I-Q plane for QPSK and the minimum Euclidian distance between signalpoints in the I-Q plane for 16QAM can be the same. Therefore, excellentreception quality can be achieved.

The condition that the minimum Euclidian distances between signal pointsin the I-Q plane for two different modulation schemes are equalized,however, is a mere example of the scheme of setting the ratio of theaverage power for QPSK to the average power for 16QAM. For example,according to other conditions such as a code length and a coding rate ofan error correction code used for error correction codes, excellentreception quality may be achieved when the value u for power change isset to a value (higher value or lower value) different from the value atwhich the minimum Euclidian distances between signal points in the I-Qplane for two different modulation schemes are equalized. Consideringthe processing efficiency, a scheme of setting the value u as shown inthe following formula is considered, for example.

[Math. 84]

u=√{square root over (2)}  (formula 84)

This will be described later in detail.

In the conventional technology, transmission power control is generallyperformed based on feedback information from a communication partner.The present invention is characterized in that the transmission power iscontrolled regardless of the feedback information from the communicationpartner in the present embodiment. Detailed description is made on thispoint.

The above describes that the value u for power change is set based onthe control signal (9900). The following describes setting of the valueu for power change based on the control signal (9900) in order toimprove data reception quality in the reception device in detail.

Example 1-1

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a block length (the number of bitsconstituting one coded block, and is also referred to as the codelength) for the error correction coding used to generate s1 and s2 whenthe transmission device supports a plurality of block lengths for theerror correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of block lengths are supported. Encoded data for which errorcorrection codes whose block length is selected from among the pluralityof supported block lengths has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected blocklength for the error correction codes described above. The power changer(9901B) sets the value u for power change according to the controlsignal (9900).

The present invention is characterized in that the power changer (9901B)sets the value u for power change according to the selected block lengthindicated by the control signal (9900). Here, a value for power changeset according to a block length X is referred to as u_(LX)

For example, when 1000 is selected as the block length, the powerchanger (9901B) sets a value for power change to u_(L1000). When 1500 isselected as the block length, the power changer (9901B) sets a value forpower change to u_(L1500). When 3000 is selected as the block length,the power changer (9901B) sets a value for power change to u_(L3000). Inthis case, for example, by setting u_(L1000), u_(L1500) and u_(L3000) soas to be different from one another, a high error correction capabilitycan be achieved for each code length. Depending on the set code length,however, the effect might not be obtained even if the value for powerchange is changed. In such a case, even when the code length is changed,it is unnecessary to change the value for power change (for example,u_(L1000)=u_(L1500) may be satisfied. What is important is that two ormore values exist in u_(L1000), u_(L1500) and u_(L1000)).

Although the case of three code lengths is taken as an example in theabove description, the present invention is not limited to this. Theimportant point is that two or more values for power change exist whenthere are two or more code lengths that can be set, and the transmissiondevice selects any of the values for power change from among the two ormore values for power change when the code length is set, and performspower change.

Example 1-2

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a coding rate for the error correctioncodes used to generate s1 and s2 when the transmission device supports aplurality of coding rates for the error correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of coding rates are supported. Encoded data for which errorcorrection codes whose coding rate is selected from among the pluralityof supported coding rates has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected codingrate for the error correction codes described above. The power changer(9901B) sets the value u for power change according to the controlsignal (9900).

The present invention is characterized in that the power changer (9901B)sets the value u for power change according to the selected coding rateindicated by the control signal (9900). Here, a value for power changeset according to a coding rate rx is referred to as u_(rX).

For example, when r1 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r1). When r2 is selected asthe coding rate, the power changer (9901B) sets a value for power changeto u_(r2). When r3 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r3). In this case, forexample, by setting u_(r1), u_(r2) and u_(r3) so as to be different fromone another, a high error correction capability can be achieved for eachcoding rate. Depending on the set coding rate, however, the effect mightnot be obtained even if the value for power change is changed. In such acase, even when the coding rate is changed, it is unnecessary to changethe value for power change (for example, u_(r1)=u_(r2) may be satisfied.What is important is that two or more values exist in u_(r1), u_(r2) andu_(r3)).

Note that, as examples of r1, r2 and r3 described above, coding rates ½,⅔ and ¾ are considered when the error correction code is the LDPC code.

Although the case of three coding rates is taken as an example in theabove description, the present invention is not limited to this. Theimportant point is that two or more values for power change exist whenthere are two or more coding rates that can be set, and the transmissiondevice selects any of the values for power change from among the two ormore values for power change when the coding rate is set, and performspower change.

Example 1-3

In order for the reception device to achieve excellent data receptionquality, it is important to implement the following.

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a modulation scheme used to generates1 and s2 when the transmission device supports a plurality ofmodulation schemes.

Here, as an example, a case where the modulation scheme for s1 is fixedto QPSK and the modulation scheme for s2 is changed from 16QAM to 64QAMby the control signal (or can be set to either 16QAM or 64QAM) isconsidered. Note that, in a case where the modulation scheme for s2(t)is 64QAM, the mapping scheme for s2(t) is as shown in FIG. 101. In FIG.101, k is represented by the following formula.

$\begin{matrix}( {{formula}\mspace{14mu} 85} ) & \; \\{k = \frac{z}{\sqrt{42}}} & \lbrack {{Math}.\mspace{14mu} 85} \rbrack\end{matrix}$

By performing mapping in this way, the average power obtained when h inFIG. 96 for QPSK is represented by formula 78 becomes equal to theaverage power obtained when g in FIG. 95 for 16QAM is represented byformula 79. In the mapping in 64QAM, the values I and Q are determinedfrom an input of six bits. In this regard, the mapping 64QAM may beperformed similarly to the mapping in QPSK and 16QAM.

That is to say, in FIG. 101 as an example of signal point layout in theI-Q plane for 64QAM, (b0, b1, b2, b3, b4, b5)=(0, 0, 0, 0, 0, 0) ismapped onto (I, Q)=(7×k, 7×k), (b0, b1, b2, b3, b4, b5)=(0, 0, 0, 0,0, 1) is mapped onto (I, Q)=(7×k, 5×k), (b0, b1, b2, b3, b4, b5)=(0, 0,0, 0, 1, 0) is mapped onto (I, Q)=(5×k, 7×k), (b0, b1, b2, b3, b4,b5)=(0, 0, 0, 0, 1, 1) is mapped onto (I, Q)=(5×k, 5×k), (b0, b1, b2,b3, b4, b5)=(0, 0, 0, 1, 0, 0) is mapped onto (I, Q)=(7×k, 1×k), . . . ,(b0, b1, b2, b3, b4, b5)=(1, 1, 1, 1, 1, 0) is mapped onto (I, Q)=(−3×k,−1×k), and (b0, b1, b2, b3, b4, b5)=(1, 1, 1, 1, 1, 1) is mapped onto(I, Q)=(−3×k, −3×k). Note that b0 through b5 shown on the top right ofFIG. 101 shows the bits and the arrangement of the numbers shown on theI-Q plane.

In FIG. 99, the power changer 9901B sets such that u=u₁₆ when themodulation scheme for s2 is 16QAM, and sets such that u=u₆₄ when themodulation scheme for s2 is 64QAM. In this case, due to the relationshipbetween minimum Euclidian distances, by setting such that u₁₆<u₆₄,excellent data reception quality is obtained in the reception devicewhen the modulation scheme for s2 is either 16QAM or 64QAM.

Note that, in the above description, the “modulation scheme for s1 isfixed to QPSK”. It is also considered that the modulation scheme for s2is fixed to QPSK. In this case, power change is assumed to be notperformed for the fixed modulation scheme (here, QPSK), and to beperformed for a plurality of modulation schemes that can be set (here,16QAM and 64QAM). That is to say, in this case, the transmission devicedoes not have the structure shown in FIG. 99, but has a structure inwhich the power changer 9901B is eliminated from the structure in FIG.99 and a power changer is provided to a s1(t)-side. When the fixedmodulation scheme (here, QPSK) is set to s2, the following formula 86 issatisfied.

$\begin{matrix}( {{formula}\mspace{14mu} 86} ) & \; \\\begin{matrix}{\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix} = {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{u\; ^{j\; 0}} & 0 \\0 & ^{j\; 0}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}u & 0 \\0 & 1\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 86} \rbrack\end{matrix}$

When the modulation scheme for s2 is fixed to QPSK and the modulationscheme for s1 is changed from 16QAM to 64QAM (is set to either 16QAM or64QAM), the relationship u₁₆<u₆₄ should be satisfied (note that amultiplied value for power change in 16QAM is u₁₆, a multiplied valuefor power change in 64QAM is u₆₄, and power change is not performed inQPSK).

Also, when a set of the modulation scheme for s1 and the modulationscheme for s2 can be set to any one of a set of QPSK and 16QAM, a set of16QAM and QPSK, a set of QPSK and 64QAM and a set of 64QAM and QPSK, therelationship u₁₆<u₆₄ should be satisfied.

The following describes a case where the above-mentioned description isgeneralized.

Let the modulation scheme for s1 be fixed to a modulation scheme C inwhich the number of signal points in the I-Q plane is c. Also, let themodulation scheme for s2 be set to either a modulation scheme A in whichthe number of signal points in the I-Q plane is a or a modulation schemeB in which the number of signal points in the I-Q plane is b (a>b>c)(however, let the average power (average value) for s2 in the modulationscheme A be equal to the average power (average value) for s2 in themodulation scheme B).

In this case, a value for power change set when the modulation scheme Ais set to the modulation scheme for s2 is u_(a). Also, a value for powerchange set when the modulation scheme B is set to the modulation schemefor s2 is u_(b). In this case, when the relationship u_(b)<u_(a) issatisfied, excellent data reception quality is obtained in the receptiondevice.

Power change is assumed to be not performed for the fixed modulationscheme (here, modulation scheme C), and to be performed for a pluralityof modulation schemes that can be set (here, modulation schemes A andB). When the modulation scheme for s2 is fixed to the modulation schemeC and the modulation scheme for s1 is changed from the modulation schemeA to the modulation scheme B (is set to either the modulation schemes Aor B), the relationship u_(b)<u_(a) should be satisfied. Also, when aset of the modulation scheme for s1 and the modulation scheme for s2 canbe set to any one of a set of the modulation scheme C and the modulationscheme A, a set of the modulation scheme A and the modulation scheme C,a set of the modulation scheme C and the modulation scheme B and a setof the modulation scheme B and the modulation scheme C, the relationshipu_(b)<u_(a) should be satisfied.

Example 2

The following describes an example of the operation different from thatdescribed in Example 1, using FIG. 99. Let s1(t) be the (mapped)baseband signal for the modulation scheme 64QAM. The mapping scheme fors1(t) is as shown in FIG. 101, and k is as represented by formula 85.Also, let s2(t) be the (mapped) baseband signal for the modulationscheme 16QAM. The mapping scheme for s2(t) is as shown in FIG. 95, and gis as represented by formula 79. Note that t is time. In the presentembodiment, description is made taking the time domain as an example.

The power changer (9901B) receives a (mapped) baseband signal 307B forthe modulation scheme 16QAM and a control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be u, the power changer outputs a signal (9902B) obtained by multiplyingthe (mapped) baseband signal 307B for the modulation scheme 16QAM by u.Let u be a real number, and u<1.0. Letting the precoding matrix used inthe scheme for regularly performing phase change on the modulated signalafter precoding be F and the phase changing value used for regularlyperforming phase change be y(t) (y(t) may be imaginary number having theabsolute value of 1, i.e. ej^(θ(t)), the following formula is satisfied.

Therefore, a ratio of the average power for 64QAM to the average powerfor 16QAM is set to 1:u². With this structure, the reception device isin a reception condition as shown in FIG. 98. Therefore, data receptionquality is improved in the reception device.

In the conventional technology, transmission power control is generallyperformed based on feedback information from a communication partner.The present invention is characterized in that the transmission power iscontrolled regardless of the feedback information from the communicationpartner in the present embodiment. Detailed description is made on thispoint.

The above describes that the value u for power change is set based onthe control signal (9900). The following describes setting of the valueu for power change based on the control signal (9900) in order toimprove data reception quality in the reception device in detail.

Example 2-1

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a block length (the number of bitsconstituting one coded block, and is also referred to as the codelength) for the error correction codes used to generate s1 and s2 whenthe transmission device supports a plurality of block lengths for theerror correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of block lengths are supported. Encoded data for which errorcorrection codes whose block length is selected from among the pluralityof supported block lengths has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected blocklength for the error correction codes described above. The power changer(9901B) sets the value u for power change according to the controlsignal (9900).

The present invention is characterized in that the power changer (9901B)sets the value u for power change according to the selected block lengthindicated by the control signal (9900). Here, a value for power changeset according to a block length X is referred to as u_(LX)

For example, when 1000 is selected as the block length, the powerchanger (9901B) sets a value for power change to u_(L1000). When 1500 isselected as the block length, the power changer (9901B) sets a value forpower change to u_(L1500). When 3000 is selected as the block length,the power changer (9901B) sets a value for power change to U_(L3000). Inthis case, for example, by setting U_(L1000), U_(L1500) and U_(L3000) soas to be different from one another, a high error correction capabilitycan be achieved for each code length. Depending on the set code length,however, the effect might not be obtained even if the value for powerchange is changed. In such a case, even when the code length is changed,it is unnecessary to change the value for power change (for example,u_(L1000)=u_(L1500) may be satisfied. What is important is that two ormore values exist in u_(L1000), u_(L1500) and u_(L1000)).

Although the case of three code lengths is taken as an example in theabove description, the present invention is not limited to this. Theimportant point is that two or more values for power change exist whenthere are two or more code lengths that can be set, and the transmissiondevice selects any of the values for power change from among the two ormore values for power change when the code length is set, and performspower change.

Example 2-2

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a coding rate for the error correctioncodes used to generate s1 and s2 when the transmission device supports aplurality of coding rates for the error correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of coding rates are supported. Encoded data for which errorcorrection codes whose coding rate is selected from among the pluralityof supported coding rates has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected codingrate for the error correction codes described above. The power changer(9901B) sets the value u for power change according to the controlsignal (9900).

The present invention is characterized in that the power changer (9901B)sets the value u for power change according to the selected coding rateindicated by the control signal (9900). Here, a value for power changeset according to a coding rate _(rx) is referred to as u_(rx).

For example, when r1 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r1). When r2 is selected asthe coding rate, the power changer (9901B) sets a value for power changeto u_(r2). When r3 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r3). In this case, forexample, by setting u_(r1), u_(r2) and u_(r3) so as to be different fromone another, a high error correction capability can be achieved for eachcoding rate. Depending on the set coding rate, however, the effect mightnot be obtained even if the value for power change is changed. In such acase, even when the coding rate is changed, it is unnecessary to changethe value for power change (for example, u_(r1)=U_(r2) may be satisfied.What is important is that two or more values exist in u_(r1), u_(r2) andu_(r3)). Note that, as examples of r1, r2 and r3 described above, codingrates ½, ⅔ and ¾ are considered when the error correction code is theLDPC code.

Although the case of three coding rates is taken as an example in theabove description, the present invention is not limited to this. Theimportant point is that two or more values for power change exist whenthere are two or more coding rates that can be set, and the transmissiondevice selects any of the values for power change from among the two ormore values for power change when the coding rate is set, and performspower change.

Example 2-3

In order for the reception device to achieve excellent data receptionquality, it is important to implement the following.

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a modulation scheme used to generates1 and s2 when the transmission device supports a plurality ofmodulation schemes.

Here, as an example, a case where the modulation scheme for s1 is fixedto 64QAM and the modulation scheme for s2 is changed from 16QAM to QPSKby the control signal (or can be set to either 16QAM or QPSK) isconsidered. In a case where the modulation scheme for s1 is 64QAM, themapping scheme for s1(t) is as shown in FIG. 101, and k is representedby formula 85 in FIG. 101. In a case where the modulation scheme for s2is 16QAM, the mapping scheme for s2(t) is as shown in FIG. 95, and g isrepresented by formula 79 in FIG. 95. Also, in a case where themodulation scheme for s2(t) is QPSK, the mapping scheme for s2(t) is asshown in FIG. 96, and h is represented by formula 78 in FIG. 96.

By performing mapping in this way, the average power in 16QAM becomesequal to the average power (average value) in QPSK.

In FIG. 99, the power changer 9901B sets such that u=u₁₆ when themodulation scheme for s2 is 16QAM, and sets such that u=u₄ when themodulation scheme for s2 is QPSK. In this case, due to the relationshipbetween minimum Euclidian distances, by setting such that u₄<u₁₆,excellent data reception quality is obtained in the reception devicewhen the modulation scheme for s2 is either 16QAM or QPSK.

Note that, in the above description, the modulation scheme for s1 isfixed to 64QAM. When the modulation scheme for s2 is fixed to 64QAM andthe modulation scheme for s1 is changed from 16QAM to QPSK (is set toeither 16QAM or QPSK), the relationship u₄<u₁₆ should be satisfied (thesame considerations should be made as the example 1-3) (note that amultiplied value for power change in 16QAM is u₁₆, a multiplied valuefor power change in QPSK is u₄, and power change is not performed in64QAM). Also, when a set of the modulation scheme for s1 and themodulation scheme for s2 can be set to any one of a set of 64QAM and16QAM, a set of 16QAM and 64QAM, a set of 64QAM and QPSK and a set ofQPSK and 64QAM, the relationship u₄<u₁₆ should be satisfied.

The following describes a case where the above-mentioned description isgeneralized.

Let the modulation scheme for s1 be fixed to a modulation scheme C inwhich the number of signal points in the I-Q plane is c. Also, let themodulation scheme for s2 be set to either a modulation scheme A in whichthe number of signal points in the I-Q plane is a or a modulation schemeB in which the number of signal points in the I-Q plane is b (c>b>a)(however, let the average power (average value) for s2 in the modulationscheme A be equal to the average power (average value) for s2 in themodulation scheme B).

In this case, a value for power change set when the modulation scheme Ais set to the modulation scheme for s2 is u_(a). Also, a value for powerchange set when the modulation scheme B is set to the modulation schemefor s2 is u_(b). In this case, when the relationship u_(a)<u_(b) issatisfied, excellent data reception quality is obtained in the receptiondevice.

Power change is assumed to be not performed for the fixed modulationscheme (here, modulation scheme C), and to be performed for a pluralityof modulation schemes that can be set (here, modulation schemes A andB). When the modulation scheme for s2 is fixed to the modulation schemeC and the modulation scheme for s1 is changed from the modulation schemeA to the modulation scheme B (is set to either the modulation schemes Aor B), the relationship u_(a)<u_(b) should be satisfied. Also, when aset of the modulation scheme for s1 and the modulation scheme for s2 canbe set to any one of a set of the modulation scheme C and the modulationscheme A, a set of the modulation scheme A and the modulation scheme C,a set of the modulation scheme C and the modulation scheme B and a setof the modulation scheme B and the modulation scheme C, the relationshipu_(a)<u_(b) should be satisfied.

Example 3

The following describes an example of the operation different from thatdescribed in Example 1, using FIG. 99. Let s1(t) be the (mapped)baseband signal for the modulation scheme 16QAM. The mapping scheme fors1(t) is as shown in FIG. 95, and g is as represented by formula 79. Lets2(t) be the (mapped) baseband signal for the modulation scheme 64QAM.The mapping scheme for s2(t) is as shown in FIG. 101, and k is asrepresented by formula 85. Note that t is time. In the presentembodiment, description is made taking the time domain as an example.

The power changer (9901B) receives a (mapped) baseband signal 307B forthe modulation scheme 64QAM and a control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be u, the power changer outputs a signal (9902B) obtained by multiplyingthe (mapped) baseband signal 307B for the modulation scheme 64QAM by u.Let u be a real number, and u>1.0. Letting the precoding matrix used inthe scheme for regularly performing phase change on the modulated signalafter precoding be F and the phase changing value used for regularlyperforming phase change be y(t) (y(t) may be imaginary number having theabsolute value of 1, i.e. ej^(θ(t)), the following formula is satisfied.

Therefore, a ratio of the average power for 16QAM to the average powerfor 64QAM is set to 1:u². With this structure, the reception device isin a reception condition as shown in FIG. 98. Therefore, data receptionquality is improved in the reception device.

In the conventional technology, transmission power control is generallyperformed based on feedback information from a communication partner.The present invention is characterized in that the transmission power iscontrolled regardless of the feedback information from the communicationpartner in the present embodiment. Detailed description is made on thispoint.

The above describes that the value u for power change is set based onthe control signal (9900). The following describes setting of the valueu for power change based on the control signal (9900) in order toimprove data reception quality in the reception device in detail.

Example 3-1

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a block length (the number of bitsconstituting one coded block, and is also referred to as the codelength) for the error correction codes used to generate s1 and s2 whenthe transmission device supports a plurality of block lengths for theerror correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of block lengths are supported. Encoded data for which errorcorrection codes whose block length is selected from among the pluralityof supported block lengths has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected blocklength for the error correction codes described above. The power changer(9901B) sets the value u for power change according to the controlsignal (9900).

The present invention is characterized in that the power changer (9901B)sets the value u for power change according to the selected block lengthindicated by the control signal (9900). Here, a value for power changeset according to a block length X is referred to as u_(LX)

For example, when 1000 is selected as the block length, the powerchanger (9901B) sets a value for power change to u_(L1000). When 1500 isselected as the block length, the power changer (9901B) sets a value forpower change to u_(L1500). When 3000 is selected as the block length,the power changer (9901B) sets a value for power change to u_(L3000). Inthis case, for example, by setting u_(L1000), u_(L1500) and u_(L3000) soas to be different from one another, a high error correction capabilitycan be achieved for each code length. Depending on the set code length,however, the effect might not be obtained even if the value for powerchange is changed. In such a case, even when the code length is changed,it is unnecessary to change the value for power change (for example,u_(L1000)=u_(L1500) may be satisfied. What is important is that two ormore values exist in u_(L1000), u_(L1500) and u_(L1000)).

Although the case of three code lengths is taken as an example in theabove description, the present invention is not limited to this. Theimportant point is that two or more values for power change exist whenthere are two or more code lengths that can be set, and the transmissiondevice selects any of the values for power change from among the two ormore values for power change when the code length is set, and performspower change.

Example 3-2

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a coding rate for the error correctioncodes used to generate s1 and s2 when the transmission device supports aplurality of coding rates for the error correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of coding rates are supported. Encoded data for which errorcorrection codes whose coding rate is selected from among the pluralityof supported coding rates has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected codingrate for the error correction codes described above. The power changer(9901B) sets the value u for power change according to the controlsignal (9900).

The present invention is characterized in that the power changer (9901B)sets the value u for power change according to the selected coding rateindicated by the control signal (9900). Here, a value for power changeset according to a coding rate rx is referred to as u_(rx).

For example, when r1 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r1). When r2 is selected asthe coding rate, the power changer (9901B) sets a value for power changeto u_(r2). When r3 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r3). In this case, forexample, by setting u_(r1), u_(r2) and u_(r3) so as to be different fromone another, a high error correction capability can be achieved for eachcoding rate. Depending on the set coding rate, however, the effect mightnot be obtained even if the value for power change is changed. In such acase, even when the coding rate is changed, it is unnecessary to changethe value for power change (for example, u_(r1)=u_(r2) may be satisfied.What is important is that two or more values exist in u_(r1), u_(r2) andu_(r3)).

Note that, as examples of r1, r2 and r3 described above, coding rates ½,⅔ and ¾ are considered when the error correction code is the LDPC code.

Although the case of three coding rates is taken as an example in theabove description, the present invention is not limited to this. Theimportant point is that two or more values for power change exist whenthere are two or more coding rates that can be set, and the transmissiondevice selects any of the values for power change from among the two ormore values for power change when the coding rate is set, and performspower change.

Example 3-3

In order for the reception device to achieve excellent data receptionquality, it is important to implement the following.

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a modulation scheme used to generates1 and s2 when the transmission device supports a plurality ofmodulation schemes.

Here, as an example, a case where the modulation scheme for s1 is fixedto 16QAM and the modulation scheme for s2 is changed from 64QAM to QPSKby the control signal (or can be set to either 64QAM or QPSK) isconsidered. In a case where the modulation scheme for s1 is 16QAM, themapping scheme for s2(t) is as shown in FIG. 95, and g is represented byformula 79 in FIG. 95. In a case where the modulation scheme for s2 is64QAM, the mapping scheme for s1(t) is as shown in FIG. 101, and k isrepresented by formula 85 in FIG. 101. Also, in a case where themodulation scheme for s2(t) is QPSK, the mapping scheme for s2(t) is asshown in FIG. 96, and h is represented by formula 78 in FIG. 96.

By performing mapping in this way, the average power in 16QAM becomesequal to the average power in QPSK.

In FIG. 99, the power changer 9901B sets such that u=u₆₄ when themodulation scheme for s2 is 64QAM, and sets such that u=u₄ when themodulation scheme for s2 is QPSK. In this case, due to the relationshipbetween minimum Euclidian distances, by setting such that u₄<u₆₄,excellent data reception quality is obtained in the reception devicewhen the modulation scheme for s2 is either 16QAM or 64QAM.

Note that, in the above description, the modulation scheme for s1 isfixed to 16QAM. When the modulation scheme for s2 is fixed to 16QAM andthe modulation scheme for s1 is changed from 64QAM to QPSK (is set toeither 64QAM or QPSK), the relationship u₄<u₆₄ should be satisfied (thesame considerations should be made as the example 1-3) (note that amultiplied value for power change in 64QAM is u₆₄, a multiplied valuefor power change in QPSK is u₄, and power change is not performed in16QAM). Also, when a set of the modulation scheme for s1 and themodulation scheme for s2 can be set to any one of a set of 16QAM and64QAM, a set of 64QAM and 16QAM, a set of 16QAM and QPSK and a set ofQPSK and 16QAM, the relationship u₄<u₆₄ should be satisfied.

The following describes a case where the above-mentioned description isgeneralized.

Let the modulation scheme for s1 be fixed to a modulation scheme C inwhich the number of signal points in the I-Q plane is c. Also, let themodulation scheme for s2 be set to either a modulation scheme A in whichthe number of signal points in the I-Q plane is a or a modulation schemeB in which the number of signal points in the I-Q plane is b (c>b>a)(however, let the average power (average value) for s2 in the modulationscheme A be equal to the average power (average value) for s2 in themodulation scheme B).

In this case, a value for power change set when the modulation scheme Ais set to the modulation scheme for s2 is u_(a). Also, a value for powerchange set when the modulation scheme B is set to the modulation schemefor s2 is u_(b). In this case, when the relationship u_(a)<u_(b) issatisfied, excellent data reception quality is obtained in the receptiondevice.

Power change is assumed to be not performed for the fixed modulationscheme (here, modulation scheme C), and to be performed for a pluralityof modulation schemes that can be set (here, modulation schemes A andB). When the modulation scheme for s2 is fixed to the modulation schemeC and the modulation scheme for s1 is changed from the modulation schemeA to the modulation scheme B (is set to either the modulation schemes Aor B), the relationship u_(a)<u_(b) should be satisfied. Also, when aset of the modulation scheme for s1 and the modulation scheme for s2 canbe set to any one of a set of the modulation scheme C and the modulationscheme A, a set of the modulation scheme A and the modulation scheme C,a set of the modulation scheme C and the modulation scheme B and a setof the modulation scheme B and the modulation scheme C, the relationshipu_(a)<u_(b) should be satisfied.

Example 4

The case where power change is performed for one of the modulationschemes for s1 and s2 has been described above. The following describesa case where power change is performed for both of the modulationschemes for s1 and s2.

An example of the operation is described using FIG. 100. Let s1(t) bethe (mapped) baseband signal for the modulation scheme QPSK. The mappingscheme for s1(t) is as shown in FIG. 96, and h is as represented byformula 78. Also, let s2(t) be the (mapped) baseband signal for themodulation scheme 16QAM. The mapping scheme for s2(t) is as shown inFIG. 95, and g is as represented by formula 79. Note that t is time. Inthe present embodiment, description is made taking the time domain as anexample.

The power changer (9901A) receives a (mapped) baseband signal 307A forthe modulation scheme QPSK and the control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be v, the power changer outputs a signal (9902A) obtained by multiplyingthe (mapped) baseband signal 307A for the modulation scheme QPSK by v.

The power changer (9901B) receives a (mapped) baseband signal 307B forthe modulation scheme 16QAM and a control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be u, the power changer outputs a signal (9902B) obtained by multiplyingthe (mapped) baseband signal 307B for the modulation scheme 16QAM by u.Then, let u=v×w (w>1.0).

Letting the precoding matrix used in the scheme for regularly performingphase change be F[t], formula 87 shown next is satisfied.

Letting the precoding matrix used in the scheme for regularly performingphase change on the modulated signal after precoding be F and the phasechanging value used for regularly performing phase change be y(t) (y(t)may be imaginary number having the absolute value of 1, i.e. ej^(θ(t)),formula 87 shown next is satisfied.

$\begin{matrix}( {{formula}\mspace{14mu} 87} ) & \; \\\begin{matrix}{\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix} = {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{v\; ^{j\; 0}} & 0 \\0 & {u\; ^{j\; 0}}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}v & 0 \\0 & u\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}v & 0 \\0 & {v \times w}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 87} \rbrack\end{matrix}$

Therefore, a ratio of the average power for QPSK to the average powerfor 16QAM is set to v²:u²=v²:v²×w²=1:w². With this structure, thereception device is in a reception condition as shown in FIG. 98.Therefore, data reception quality is improved in the reception device.

In the conventional technology, transmission power control is generallyperformed based on feedback information from a communication partner.The present invention is characterized in that the transmission power iscontrolled regardless of the feedback information from the communicationpartner in the present embodiment. Detailed description is made on thispoint.

The above describes that the values v and u for power change are setbased on the control signal (9900). The following describes setting ofthe values v and u for power change based on the control signal (9900)in order to improve data reception quality in the reception device indetail.

Example 4-1

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a block length (the number of bitsconstituting one coded block, and is also referred to as the codelength) for the error correction codes used to generate s1 and s2 whenthe transmission device supports a plurality of block lengths for theerror correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of block lengths are supported. Encoded data for which errorcorrection codes whose block length is selected from among the pluralityof supported block lengths has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected blocklength for the error correction codes described above. The power changer(9901B) sets the value v for power change according to the controlsignal (9900). Similarly, the power changer (9901B) sets the value u forpower change according to the control signal (9900).

The present invention is characterized in that the power changers (9901Aand 9901B) respectively set the values v and u for power changeaccording to the selected block length indicated by the control signal(9900). Here, values for power change set according to the block lengthX are referred to as v_(LX) and u_(LX).

For example, when 1000 is selected as the block length, the powerchanger (9901A) sets a value for power change to v_(L1000). When 1500 isselected as the block length, the power changer (9901A) sets a value forpower change to v_(L1500). When 3000 is selected as the block length,the power changer (9901A) sets a value for power change to v_(L3000).

On the other hand, when 1000 is selected as the block length, the powerchanger (9901B) sets a value for power change to u_(L1000). When 1500 isselected as the block length, the power changer (9901B) sets a value forpower change to u_(L1500). When 3000 is selected as the block length,the power changer (9901B) sets a value for power change to u_(L3000).

In this case, for example, by setting v_(L1000), v_(L1500) and v_(L3000)so as to be different from one another, a high error correctioncapability can be achieved for each code length. Similarly, by settingu_(L1000), u_(L1500) and u_(L3000) so as to be different from oneanother, a high error correction capability can be achieved for eachcode length. Depending on the set code length, however, the effect mightnot be obtained even if the value for power change is changed. In such acase, even when the code length is changed, it is unnecessary to changethe value for power change (for example, u_(L1000)=u_(L1500) may besatisfied, and v_(L1000)=v_(L1500) may be satisfied. What is importantis that two or more values exist in a set of v_(L1000), v_(L1500) andv_(L3000), and that two or more values exist in a set of u_(L1000),u_(L1500) and u_(L3000)). Note that, as described above, v_(LX) andu_(LX) are set so as to satisfy the ratio of the average power 1:w².

Although the case of three code lengths is taken as an example in theabove description, the present invention is not limited to this. Oneimportant point is that two or more values u_(LX) for power change existwhen there are two or more code lengths that can be set, and thetransmission device selects any of the values for power change fromamong the two or more values u_(LX) for power change when the codelength is set, and performs power change. Another important point isthat two or more values v_(LX) for power change exist when there are twoor more code lengths that can be set, and the transmission deviceselects any of the values for power change from among the two or morevalues v_(LX) for power change when the code length is set, and performspower change.

Example 4-2

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a coding rate for the error correctioncodes used to generate s1 and s2 when the transmission device supports aplurality of coding rates for the error correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of coding rates are supported. Encoded data for which errorcorrection codes whose coding rate is selected from among the pluralityof supported coding rates has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected codingrate for the error correction codes described above. The power changer(9901A) sets the value v for power change according to the controlsignal (9900). Similarly, the power changer (9901B) sets the value u forpower change according to the control signal (9900).

The present invention is characterized in that the power changers (9901Aand 9901B) respectively set the values v and u for power changeaccording to the selected coding rate indicated by the control signal(9900). Here, values for power change set according to the coding raterx are referred to as v_(rx) and u_(rx).

For example, when r1 is selected as the coding rate, the power changer(9901A) sets a value for power change to v_(r1). When r2 is selected asthe coding rate, the power changer (9901A) sets a value for power changeto v_(r2). When r3 is selected as the coding rate, the power changer(9901A) sets a value for power change to v_(r3).

Also, when r1 is selected as the coding rate, the power changer (9901B)sets a value for power change to u_(r1). When r2 is selected as thecoding rate, the power changer (9901B) sets a value for power change tou_(r2). When r3 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r3).

In this case, for example, by setting v_(r1), v_(r2) and v_(r3) so as tobe different from one another, a high error correction capability can beachieved for each code length. Similarly, by setting u_(r1), u_(r2) andu_(r3) so as to be different from one another, a high error correctioncapability can be achieved for each coding rate. Depending on the setcoding rate, however, the effect might not be obtained even if the valuefor power change is changed. In such a case, even when the coding rateis changed, it is unnecessary to change the value for power change (forexample, v_(r1)=v_(r2) may be satisfied, and u_(r1)=u_(r2) may besatisfied. What is important is that two or more values exist in a setof v_(r1), v_(r2) and v_(r3), and that two or more values exist in a setof u_(r1), u_(r2) and u_(r3)). Note that, as described above, v_(rX) andu_(rX) are set so as to satisfy the ratio of the average power 1:w².

Also, note that, as examples of r1, r2 and r3 described above, codingrates ½, ⅔ and ¾ are considered when the error correction code is theLDPC code.

Although the case of three coding rates is taken as an example in theabove description, the present invention is not limited to this. Oneimportant point is that two or more values u_(rx) for power change existwhen there are two or more coding rates that can be set, and thetransmission device selects any of the values for power change fromamong the two or more values u_(rx) for power change when the codingrate is set, and performs power change. Another important point is thattwo or more values v_(rX) for power change exist when there are two ormore coding rates that can be set, and the transmission device selectsany of the values for power change from among the two or more valuesv_(rX) for power change when the coding rate is set, and performs powerchange.

Example 4-3

In order for the reception device to achieve excellent data receptionquality, it is important to implement the following.

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a modulation scheme used to generates1 and s2 when the transmission device supports a plurality ofmodulation schemes.

Here, as an example, a case where the modulation scheme for s1 is fixedto QPSK and the modulation scheme for s2 is changed from 16QAM to 64QAMby the control signal (or can be set to either 16QAM or 64QAM) isconsidered. In a case where the modulation scheme for s1 is QPSK, themapping scheme for s1(t) is as shown in FIG. 96, and h is represented byformula 78 in FIG. 96. In a case where the modulation scheme for s2 is16QAM, the mapping scheme for s2(t) is as shown in FIG. 95, and g isrepresented by formula 79 in FIG. 95. Also, in a case where themodulation scheme for s2(t) is 64QAM, the mapping scheme for s2(t) is asshown in FIG. 101, and k is represented by formula 85 in FIG. 101.

In FIG. 100, when the modulation scheme for s1 is QPSK and themodulation scheme for s2 is 16QAM, assume that v=α and u=α×w₁₆. In thiscase, the ratio between the average power of QPSK and the average powerof 16QAM is v²:u²=α²:α²×w₁₆ ²=1:w₁₆ ².

In FIG. 100, when the modulation scheme for s1 is QPSK and themodulation scheme for s2 is 64QAM, assume that v=β and u=β×w₆₄. In thiscase, the ratio between the average power of QPSK and the average powerof 64QAM is v:u=β²:β²×w₆₄ ²=1:w₆₄ ². In this case, according to theminimum Euclidean distance relationship, the reception device achieveshigh data reception quality when 1.0<w₁₆<w₆₄, regardless of whether themodulation scheme for s2 is 16QAM or 64QAM.

Note that although “the modulation scheme for s1 is fixed to QPSK” inthe description above, it is possible that “the modulation scheme for s2is fixed to QPSK”. In this case, power change is assumed to be notperformed for the fixed modulation scheme (here, QPSK), and to beperformed for a plurality of modulation schemes that can be set (here,16QAM and 64QAM). When the fixed modulation scheme (here, QPSK) is setto s2, the following formula 88 is satisfied.

$\begin{matrix}( {{formula}\mspace{14mu} 88} ) & \; \\\begin{matrix}{\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix} = {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{u\; ^{j\; 0}} & 0 \\0 & {v\; ^{j\; 0}}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}u & 0 \\0 & v\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{v \times w} & 0 \\0 & v\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 88} \rbrack\end{matrix}$

Given that, even when “the modulation scheme for s2 is fixed to QPSK andthe modulation scheme for s1 is changed from 16QAM to 64QAM (set toeither 16QAM or 64QAM)”, 1.0<w₁₆<w₆₄ should be fulfilled. (Note that thevalue used for the multiplication for the power change in the case of16QAM is u=α×w₁₆, the value used for the multiplication for the powerchange in the case of 64QAM is u=β×w₆₄, the value used for the powerchange in the case of QPSK is v=a when the selectable modulation schemeis 16QAM and v=β when the selectable modulation scheme is 64QAM.) Also,when the set of (the modulation scheme for s1, the modulation scheme fors2) is selectable from the sets of (QPSK, 16QAM), (16QAM, QPSK), (QPSK,64QAM) and (64QAM, QPSK), 1.0<w₁₆<w₆₄ should be fulfilled.

The following describes a case where the above-mentioned description isgeneralized.

For generalization, assume that the modulation scheme for s1 is fixed toa modulation scheme C with which the number of signal points in the I-Qplane is c. Also assume that the modulation scheme for s2 is selectablefrom a modulation scheme A with which the number of signal points in theI-Q plane is a and a modulation scheme B with which the number of signalpoints in the I-Q plane is b (a>b>c). In this case, when the modulationscheme for s2 is set to the modulation scheme A, assume that ratiobetween the average power of the modulation scheme for s1, which is themodulation scheme C, and the average power of the modulation scheme fors2, which is the modulation scheme A, is 1:w_(a) ². Also, when themodulation scheme for s2 is set to the modulation scheme B, assume thatratio between the average power of the modulation scheme for s1, whichis the modulation scheme C, and the average power of the modulationscheme for s2, which is the modulation scheme B, is 1:w_(b) ². If thisis the case, the reception device achieves a high data reception qualitywhen w_(b)<w_(a) is fulfilled.

Note that although “the modulation scheme for s1 is fixed to C” in thedescription above, even when “the modulation scheme for s2 is fixed tothe modulation scheme C and the modulation scheme for s1 is changed fromthe modulation scheme A to the modulation scheme B (set to either themodulation scheme A or the modulation scheme B), the average powersshould fulfill w_(b)<w_(a). (If this is the case, as with thedescription above, when the average power of the modulation scheme C is1, the average power of the modulation scheme A is w_(a) ^(g), and theaverage power of the modulation scheme B is w_(b) ².) Also, when the setof (the modulation scheme for s1, the modulation scheme for s2) isselectable from the sets of (the modulation scheme C, the modulationscheme A), (the modulation scheme A, the modulation scheme C), (themodulation scheme C, the modulation scheme B) and (the modulation schemeB, the modulation scheme C), the average powers should fulfillw_(b)<w_(a).

Example 5

The following describes an example of the operation different from thatdescribed in Example 4, using FIG. 100. Let s1(t) be the (mapped)baseband signal for the modulation scheme 64QAM. The mapping scheme fors1(t) is as shown in FIG. 86, and k is as represented by formula 85.Also, let s2(t) be the (mapped) baseband signal for the modulationscheme 16QAM. The mapping scheme for s2(t) is as shown in FIG. 95, and gis as represented by formula 79. Note that t is time. In the presentembodiment, description is made taking the time domain as an example.

The power changer (9901A) receives a (mapped) baseband signal 307A forthe modulation scheme 64QAM and the control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be v, the power changer outputs a signal (9902A) obtained by multiplyingthe (mapped) baseband signal 307A for the modulation scheme 64QAM by v.

The power changer (9901B) receives a (mapped) baseband signal 307B forthe modulation scheme 16QAM and a control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be u, the power changer outputs a signal (9902B) obtained by multiplyingthe (mapped) baseband signal 307B for the modulation scheme 16QAM by u.Then, let u=v×w (w<1.0).

Letting the precoding matrix used in the scheme for regularly performingphase change on the modulated signal after precoding be F and the phasechanging value used for regularly performing phase change be y(t) (y(t)may be imaginary number having the absolute value of 1, i.e. ej^(θ(t)),formula 87 shown above is satisfied.

Therefore, a ratio of the average power for 64QAM to the average powerfor 16QAM is set to v²:u²=v²:v²×w²=1:w². With this structure, thereception device is in a reception condition as shown in FIG. 98.Therefore, data reception quality is improved in the reception device.

In the conventional technology, transmission power control is generallyperformed based on feedback information from a communication partner.The present invention is characterized in that the transmission power iscontrolled regardless of the feedback information from the communicationpartner in the present embodiment. Detailed description is made on thispoint.

The above describes that the values v and u for power change are setbased on the control signal (9900). The following describes setting ofthe values v and u for power change based on the control signal (9900)in order to improve data reception quality in the reception device indetail.

Example 5-1

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a block length (the number of bitsconstituting one coded block, and is also referred to as the codelength) for the error correction codes used to generate s1 and s2 whenthe transmission device supports a plurality of block lengths for theerror correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of block lengths are supported. Encoded data for which errorcorrection codes whose block length is selected from among the pluralityof supported block lengths has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected blocklength for the error correction codes described above. The power changer(9901B) sets the value v for power change according to the controlsignal (9900). Similarly, the power changer (9901B) sets the value u forpower change according to the control signal (9900).

The present invention is characterized in that the power changers (9901Aand 9901B) respectively set the values v and u for power changeaccording to the selected block length indicated by the control signal(9900). Here, values for power change set according to the block lengthX are referred to as v_(LX) and u_(LX).

For example, when 1000 is selected as the block length, the powerchanger (9901A) sets a value for power change to v_(L1000). When 1500 isselected as the block length, the power changer (9901A) sets a value forpower change to v_(L1500). When 3000 is selected as the block length,the power changer (9901A) sets a value for power change to v_(L3000).

On the other hand, when 1000 is selected as the block length, the powerchanger (9901B) sets a value for power change to u_(L1000). When 1500 isselected as the block length, the power changer (9901B) sets a value forpower change to u_(L1500). When 3000 is selected as the block length,the power changer (9901B) sets a value for power change to u_(L3000).

In this case, for example, by setting v_(L1000), v_(L1500) and v_(L3000)so as to be different from one another, a high error correctioncapability can be achieved for each code length. Similarly, by settingu_(L1000), u_(L1500) and u_(L3000) so as to be different from oneanother, a high error correction capability can be achieved for eachcode length. Depending on the set code length, however, the effect mightnot be obtained even if the value for power change is changed. In such acase, even when the code length is changed, it is unnecessary to changethe value for power change (for example, u_(L1000)=u_(L1500) may besatisfied, and v_(L1000)=v_(L1500) may be satisfied. What is importantis that two or more values exist in a set of v_(L1000), v_(L1500) andv_(L3000), and that two or more values exist in a set of u_(L1000),u_(L1500) and u_(L3000)). Note that, as described above, v_(LX) andu_(LX) are set so as to satisfy the ratio of the average power 1:w².

Although the case of three code lengths is taken as an example in theabove description, the present invention is not limited to this. Oneimportant point is that two or more values u_(LX) for power change existwhen there are two or more code lengths that can be set, and thetransmission device selects any of the values for power change fromamong the two or more values u_(LX) for power change when the codelength is set, and performs power change. Another important point isthat two or more values v_(LX) for power change exist when there are twoor more code lengths that can be set, and the transmission deviceselects any of the values for power change from among the two or morevalues v_(LX) for power change when the code length is set, and performspower change.

Example 5-2

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a coding rate for the error correctioncodes used to generate s1 and s2 when the transmission device supports aplurality of coding rates for the error correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of coding rates are supported. Encoded data for which errorcorrection codes whose coding rate is selected from among the pluralityof supported coding rates has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected codingrate for the error correction codes described above. The power changer(9901A) sets the value v for power change according to the controlsignal (9900). Similarly, the power changer (9901B) sets the value u forpower change according to the control signal (9900).

The present invention is characterized in that the power changers (9901Aand 9901B) respectively set the values v and u for power changeaccording to the selected coding rate indicated by the control signal(9900). Here, values for power change set according to the coding raterx are referred to as v_(rx) and u_(rx).

For example, when r1 is selected as the coding rate, the power changer(9901A) sets a value for power change to v_(r1). When r2 is selected asthe coding rate, the power changer (9901A) sets a value for power changeto v_(r2). When r3 is selected as the coding rate, the power changer(9901A) sets a value for power change to v_(r3).

Also, when r1 is selected as the coding rate, the power changer (9901B)sets a value for power change to u_(r1). When r2 is selected as thecoding rate, the power changer (9901B) sets a value for power change tou_(r2). When r3 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r3).

In this case, for example, by setting v_(r1), v_(a) and v_(r3) so as tobe different from one another, a high error correction capability can beachieved for each code length. Similarly, by setting u_(r1), u_(r2) andu_(r3) so as to be different from one another, a high error correctioncapability can be achieved for each coding rate. Depending on the setcoding rate, however, the effect might not be obtained even if the valuefor power change is changed. In such a case, even when the coding rateis changed, it is unnecessary to change the value for power change (forexample, v_(r1)=v_(r2) may be satisfied, and u_(r1)=u_(r2) may besatisfied. What is important is that two or more values exist in a setof v_(r1), v_(r2) and v_(r3), and that two or more values exist in a setof u_(r1), u_(r2) and u_(r3)). Note that, as described above, v_(rX) andu_(rX) are set so as to satisfy the ratio of the average power 1:w².

Also, note that, as examples of r1, r2 and r3 described above, codingrates ½, ⅔ and ¾ are considered when the error correction code is theLDPC code.

Although the case of three coding rates is taken as an example in theabove description, the present invention is not limited to this. Oneimportant point is that two or more values u_(rx) for power change existwhen there are two or more coding rates that can be set, and thetransmission device selects any of the values for power change fromamong the two or more values u_(rx) for power change when the codingrate is set, and performs power change. Another important point is thattwo or more values v_(rX) for power change exist when there are two ormore coding rates that can be set, and the transmission device selectsany of the values for power change from among the two or more valuesv_(rX) for power change when the coding rate is set, and performs powerchange.

Example 5-3

In order for the reception device to achieve excellent data receptionquality, it is important to implement the following.

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a modulation scheme used to generates1 and s2 when the transmission device supports a plurality ofmodulation schemes.

Here, as an example, a case where the modulation scheme for s1 is fixedto 64QAM and the modulation scheme for s2 is changed from 16QAM to QPSKby the control signal (or can be set to either 16QAM or QPSK) isconsidered. In a case where the modulation scheme for s1 is 64QAM, themapping scheme for s1(t) is as shown in FIG. 101, and k is representedby formula 85 in FIG. 101. In a case where the modulation scheme for s2is 16QAM, the mapping scheme for s2(t) is as shown in FIG. 95, and g isrepresented by formula 79 in FIG. 95. Also, in a case where themodulation scheme for s2(t) is QPSK, the mapping scheme for s2(t) is asshown in FIG. 96, and h is represented by formula 78 in FIG. 96.

In FIG. 100, when the modulation scheme for s1 is 64QAM and themodulation scheme for s2 is 16QAM, assume that v=α and u=α×w₁₆. In thiscase, the ratio between the average power of 64QAM and the average powerof 16QAM is v²:u²=α²:α²×w₁₆ ²=1:w₁₆ ².

In FIG. 100, when the modulation scheme for s1 is 64QAM and themodulation scheme for s2 is QPSK, assume that v=β and u=β×w₄. In thiscase, the ratio between the average power of 64QAM and the average powerof QPSK is v²:u²=β²:β²×w₄ ²=1:w₄ ². In this case, according to theminimum Euclidean distance relationship, the reception device achieves ahigh data reception quality when w₄<w₁₆<1.0, regardless of whether themodulation scheme for s2 is 16QAM or QPSK.

Note that although “the modulation scheme for s1 is fixed to 64QAM” inthe description above, it is possible that “the modulation scheme for s2is fixed to 64QAM and the modulation scheme for s1 is changed from 16QAMto QPSK (set to either 16QAM or QPSK)”, w₄<w₁₆<1.0 should be fulfilled.(The same as described in Example 4-3). (Note that the value used forthe multiplication for the power change in the case of 16QAM is u=α×w₁₆,the value used for the multiplication for the power change in the caseof QPSK is u=β×w₄, the value used for the power change in the case of64QAM is v=a when the selectable modulation scheme is 16QAM and v=β whenthe selectable modulation scheme is QPSK). Also, when the set of (themodulation scheme for s1, the modulation scheme for s2) is selectablefrom the sets of (64QAM, 16QAM), (16QAM, 64QAM), (64QAM, QPSK) and(QPSK, 64QAM), w₄<w₁₆<1.0 should be fulfilled.

The following describes a case where the above-mentioned description isgeneralized.

For generalization, assume that the modulation scheme for s1 is fixed toa modulation scheme C with which the number of signal points in the I-Qplane is c. Also assume that the modulation scheme for s2 is selectablefrom a modulation scheme A with which the number of signal points in theI-Q plane is a and a modulation scheme B with which the number of signalpoints in the I-Q plane is b (c>b>a). In this case, when the modulationscheme for s2 is set to the modulation scheme A, assume that ratiobetween the average power of the modulation scheme for s1, which is themodulation scheme C, and the average power of the modulation scheme fors2, which is the modulation scheme A, is 1:w_(a) ². Also, when themodulation scheme for s2 is set to the modulation scheme B, assume thatratio between the average power of the modulation scheme for s1, whichis the modulation scheme C, and the average power of the modulationscheme for s2, which is the modulation scheme B, is 1:w_(b) ². If thisis the case, the reception device achieves a high data reception qualitywhen w_(a)<w_(b) is fulfilled.

Note that although “the modulation scheme for s1 is fixed to C” in thedescription above, even when “the modulation scheme for s2 is fixed tothe modulation scheme C and the modulation scheme for s1 is changed fromthe modulation scheme A to the modulation scheme B (set to either themodulation scheme A or the modulation scheme B), the average powersshould fulfill w_(a)<w_(b). (If this is the case, as with thedescription above, when the average power of the modulation scheme is C,the average power of the modulation scheme A is w_(a) ^(g), and theaverage power of the modulation scheme B is w_(b) ².) Also, when the setof (the modulation scheme for s1, the modulation scheme for s2) isselectable from the sets of (the modulation scheme C, the modulationscheme A), (the modulation scheme A, the modulation scheme C), (themodulation scheme C, the modulation scheme B) and (the modulation schemeB, the modulation scheme C), the average powers should fulfillw_(a)<w_(b).

Example 6

The following describes an example of the operation different from thatdescribed in Example 4, using FIG. 100. Let s1(t) be the (mapped)baseband signal for the modulation scheme 16QAM. The mapping scheme fors1(t) is as shown in FIG. 101, and g is as represented by formula 79.Let s2(t) be the (mapped) baseband signal for the modulation scheme64QAM. The mapping scheme for s2(t) is as shown in FIG. 101, and k is asrepresented by formula 85. Note that t is time. In the presentembodiment, description is made taking the time domain as an example.

The power changer (9901A) receives a (mapped) baseband signal 307A forthe modulation scheme 16QAM and the control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be v, the power changer outputs a signal (9902A) obtained by multiplyingthe (mapped) baseband signal 307A for the modulation scheme 16QAM by v.

The power changer (9901B) receives a (mapped) baseband signal 307B forthe modulation scheme 64QAM and a control signal (9900) as input.Letting a value for power change set based on the control signal (9900)be u, the power changer outputs a signal (9902B) obtained by multiplyingthe (mapped) baseband signal 307B for the modulation scheme 64QAM by u.Then, let u=v×w (w<1.0).

Letting the precoding matrix used in the scheme for regularly performingphase change on the modulated signal after precoding be F and the phasechanging value used for regularly performing phase change be y(t) (y(t)may be imaginary number having the absolute value of 1, i.e. ej^(θ(t)),formula 87 shown above is satisfied.

Therefore, a ratio of the average power for 64QAM to the average powerfor 16QAM is set to v²:u²=v²:v²×w²=1:w². With this structure, thereception device is in a reception condition as shown in FIG. 98.Therefore, data reception quality is improved in the reception device.

In the conventional technology, transmission power control is generallyperformed based on feedback information from a communication partner.The present invention is characterized in that the transmission power iscontrolled regardless of the feedback information from the communicationpartner in the present embodiment. Detailed description is made on thispoint.

The above describes that the values v and u for power change are setbased on the control signal (9900). The following describes setting ofthe values v and u for power change based on the control signal (9900)in order to improve data reception quality in the reception device indetail.

Example 6-1

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a block length (the number of bitsconstituting one coded block, and is also referred to as the codelength) for the error correction codes used to generate s1 and s2 whenthe transmission device supports a plurality of block lengths for theerror correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of block lengths are supported. Encoded data for which errorcorrection codes whose block length is selected from among the pluralityof supported block lengths has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected blocklength for the error correction codes described above. The power changer(9901B) sets the value v for power change according to the controlsignal (9900). Similarly, the power changer (9901B) sets the value u forpower change according to the control signal (9900).

The present invention is characterized in that the power changers (9901Aand 9901B) respectively set the values v and u for power changeaccording to the selected block length indicated by the control signal(9900). Here, values for power change set according to the block lengthX are referred to as v_(LX) and u_(LX).

For example, when 1000 is selected as the block length, the powerchanger (9901A) sets a value for power change to v_(L1000). When 1500 isselected as the block length, the power changer (9901A) sets a value forpower change to v_(L1500). When 3000 is selected as the block length,the power changer (9901A) sets a value for power change to v_(L3000).

On the other hand, when 1000 is selected as the block length, the powerchanger (9901B) sets a value for power change to u_(L1000). When 1500 isselected as the block length, the power changer (9901B) sets a value forpower change to u_(L1500). When 3000 is selected as the block length,the power changer (9901B) sets a value for power change to u_(L3000).

In this case, for example, by setting v_(L1000), v_(L1500) and v_(L3000)so as to be different from one another, a high error correctioncapability can be achieved for each code length. Similarly, by settingu_(L1000), u_(L1500) and u_(L3000) so as to be different from oneanother, a high error correction capability can be achieved for eachcode length. Depending on the set code length, however, the effect mightnot be obtained even if the value for power change is changed. In such acase, even when the code length is changed, it is unnecessary to changethe value for power change (for example, u_(L1000)=u_(L1500) may besatisfied, and v_(L1000)=v_(L1500) may be satisfied. What is importantis that two or more values exist in a set of v_(L1000), v_(L1500) andv_(L3000), and that two or more values exist in a set of u_(L1000),u_(L1500) and u_(L3000)). Note that, as described above, v_(LX) andu_(LX) are set so as to satisfy the ratio of the average power 1:w².

Although the case of three code lengths is taken as an example in theabove description, the present invention is not limited to this. Oneimportant point is that two or more values u_(LX) for power change existwhen there are two or more code lengths that can be set, and thetransmission device selects any of the values for power change fromamong the two or more values u_(LX) for power change when the codelength is set, and performs power change. Another important point isthat two or more values v_(LX) for power change exist when there are twoor more code lengths that can be set, and the transmission deviceselects any of the values for power change from among the two or morevalues v_(LX) for power change when the code length is set, and performspower change.

Example 6-2

The following describes a scheme of setting the average power of s1 ands2 according to a coding rate for the error correction codes used togenerate s1 and s2 when the transmission device supports a plurality ofcoding rates for the error correction codes.

Examples of the error correction codes include block codes such as Turbocodes or Duo-Binary Turbo codes using tail-biting, LDPC codes, or thelike. In many communication systems and broadcasting systems, aplurality of coding rates are supported. Encoded data for which errorcorrection codes whose coding rate is selected from among the pluralityof supported coding rates has been performed is distributed to twosystems. The encoded data having been distributed to the two systems ismodulated in the modulation scheme for s1 and in the modulation schemefor s2 to generate the (mapped) baseband signals s1(t) and s2(t).

The control signal (9900) is a signal indicating the selected codingrate for the error correction codes described above. The power changer(9901A) sets the value v for power change according to the controlsignal (9900). Similarly, the power changer (9901B) sets the value u forpower change according to the control signal (9900).

The present invention is characterized in that the power changers (9901Aand 9901B) respectively set the values v and u for power changeaccording to the selected coding rate indicated by the control signal(9900). Here, values for power change set according to the coding raterx are referred to as v_(rx) and u_(rx).

For example, when r1 is selected as the coding rate, the power changer(9901A) sets a value for power change to v_(r1). When r2 is selected asthe coding rate, the power changer (9901A) sets a value for power changeto v_(r2). When r3 is selected as the coding rate, the power changer(9901A) sets a value for power change to v_(r3).

Also, when r1 is selected as the coding rate, the power changer (9901B)sets a value for power change to u_(r1). When r2 is selected as thecoding rate, the power changer (9901B) sets a value for power change tou_(r2). When r3 is selected as the coding rate, the power changer(9901B) sets a value for power change to u_(r3).

In this case, for example, by setting v_(r1), v_(r2) and v_(r3) so as tobe different from one another, a high error correction capability can beachieved for each code length. Similarly, by setting u_(r1), u_(r2) andu_(r3) so as to be different from one another, a high error correctioncapability can be achieved for each coding rate. Depending on the setcoding rate, however, the effect might not be obtained even if the valuefor power change is changed. In such a case, even when the coding rateis changed, it is unnecessary to change the value for power change (forexample, v_(r1)=v_(r2) may be satisfied, and u_(r1)=u_(r2) may besatisfied. What is important is that two or more values exist in a setof v_(r1), v_(r2) and v_(r3), and that two or more values exist in a setof u_(r1), u_(r2) and u_(r3)). Note that, as described above, v_(rX) andu_(rX) are set so as to satisfy the ratio of the average power 1:w².

Also, note that, as examples of r1, r2 and r3 described above, codingrates ½, ⅔ and ¾ are considered when the error correction code is theLDPC code.

Although the case of three coding rates is taken as an example in theabove description, the present invention is not limited to this. Oneimportant point is that two or more values u_(rx) for power change existwhen there are two or more coding rates that can be set, and thetransmission device selects any of the values for power change fromamong the two or more values u_(rx) for power change when the codingrate is set, and performs power change. Another important point is thattwo or more values v_(rX) for power change exist when there are two ormore coding rates that can be set, and the transmission device selectsany of the values for power change from among the two or more valuesv_(rX) for power change when the coding rate is set, and performs powerchange.

Example 6-3

In order for the reception device to achieve excellent data receptionquality, it is important to implement the following.

The following describes a scheme of setting the average power (averagevalues) of s1 and s2 according to a modulation scheme used to generates1 and s2 when the transmission device supports a plurality ofmodulation schemes.

Here, as an example, a case where the modulation scheme for s1 is fixedto 16QAM and the modulation scheme for s2 is changed from 64QAM to QPSKby the control signal (or can be set to either 16QAM or QPSK) isconsidered. In a case where the modulation scheme for s1 is 16QAM, themapping scheme for s1(t) is as shown in FIG. 95, and g is represented byformula 79 in FIG. 95. In a case where the modulation scheme for s2 is64QAM, the mapping scheme for s2(t) is as shown in FIG. 101, and k isrepresented by formula 85 in FIG. 101. Also, in a case where themodulation scheme for s2(t) is QPSK, the mapping scheme for s2(t) is asshown in FIG. 96, and h is represented by formula 78 in FIG. 96.

In FIG. 100, when the modulation scheme for s1 is 16QAM and themodulation scheme for s2 is 64QAM, assume that v=α and u=α×w₆₄. In thiscase, the ratio between the average power of 64QAM and the average powerof 16QAM is v²:u²=α²:α²×w₆₄ ²=1:w₆₄ ².

In FIG. 100, when the modulation scheme for s1 is 16QAM and themodulation scheme for s2 is QPSK, assume that v=β and u=β×w₄. In thiscase, the ratio between the average power of 64QAM and the average powerof QPSK is v²:u²=β²:β²×w₄ ²=1:w₄ ². In this case, according to theminimum Euclidean distance relationship, the reception device achieves ahigh data reception quality when w₄<w₆₄, regardless of whether themodulation scheme for s2 is 64QAM or QPSK.

Note that although “the modulation scheme for s1 is fixed to 16QAM” inthe description above, it is possible that “the modulation scheme for s2is fixed to 16QAM and the modulation scheme for s1 is changed from 64QAMto QPSK (set to either 16QAM or QPSK)”, w₄<w64 should be fulfilled. (Thesame as described in Example 4-3). (Note that the value used for themultiplication for the power change in the case of 16QAM is u=α×w₁₆, thevalue used for the multiplication for the power change in the case ofQPSK is u=β×w₄, the value used for the power change in the case of 64QAMis v=a when the selectable modulation scheme is 16QAM and v=β when theselectable modulation scheme is QPSK). Also, when the set of (themodulation scheme for s1, the modulation scheme for s2) is selectablefrom the sets of (16QAM, 64QAM), (64QAM, 16QAM), (16QAM, QPSK) and(QPSK, 16QAM), w₄<w₆₄ should be fulfilled.

The following describes a case where the above-mentioned description isgeneralized.

For generalization, assume that the modulation scheme for s1 is fixed toa modulation scheme C with which the number of signal points in the I-Qplane is c. Also assume that the modulation scheme for s2 is selectablefrom a modulation scheme A with which the number of signal points in theI-Q plane is a and a modulation scheme B with which the number of signalpoints in the I-Q plane is b (c>b>a). In this case, when the modulationscheme for s2 is set to the modulation scheme A, assume that ratiobetween the average power of the modulation scheme for s1, which is themodulation scheme C, and the average power of the modulation scheme fors2, which is the modulation scheme A, is 1:w_(a) ². Also, when themodulation scheme for s2 is set to the modulation scheme B, assume thatratio between the average power of the modulation scheme for s1, whichis the modulation scheme C, and the average power of the modulationscheme for s2, which is the modulation scheme B, is 1:w_(b) ². If thisis the case, the reception device achieves a high data reception qualitywhen w_(a)<w_(b) is fulfilled.

Note that although “the modulation scheme for s1 is fixed to C” in thedescription above, even when “the modulation scheme for s2 is fixed tothe modulation scheme C and the modulation scheme for s1 is changed fromthe modulation scheme A to the modulation scheme B (set to either themodulation scheme A or the modulation scheme B), the average powersshould fulfill w_(a)<w_(b). (If this is the case, as with thedescription above, when the average power of the modulation scheme is C,the average power of the modulation scheme A is w_(a) ^(g), and theaverage power of the modulation scheme B is w_(b) ².) Also, when the setof (the modulation scheme for s1 and the modulation scheme for s2) isselectable from the sets of (the modulation scheme C and the modulationscheme A), (the modulation scheme A and the modulation scheme C), (themodulation scheme C and the modulation scheme B) and (the modulationscheme B and the modulation scheme C), the average powers should fulfillw_(a)<w_(b).

In the present description including “Embodiment 1”, and so on, thepower consumption by the transmission device can be reduced by settingα=1 in the formula 36 representing the precoding matrices used for thescheme for regularly changing the phase. This is because the averagepower of z1 and the average power of z2 are the same even when “theaverage power (average value) of s1 and the average power (averagevalue) of s2 are set to be different when the modulation scheme for s1and the modulation scheme for s2 are different”, and setting α=1 doesnot result in increasing the PAPR (Peak-to-Average Power Ratio) of thetransmission power amplifier provided in the transmission device.

However, even when α≠1, there are some precoding matrices that can beused with the scheme that regularly changes the phase and have limitedinfluence to PAPR. For example, when the precoding matrices representedby formula 36 in Embodiment 1 are used to achieve the scheme forregularly changing the phase, the precoding matrices have limitedinfluence to PAPR even when α≠1.

Operations of the Reception Device

Subsequently, explanation is provided of the operations of the receptiondevice. Explanation of the reception device has already been provided inEmbodiment 1 and so on, and the structure of the reception device isillustrated in FIGS. 7, 8, 9, 86, 87 and 88, for instance

According to the relation illustrated in FIG. 5, when the transmissiondevice transmits modulated signals as introduced in FIGS. 99 and 100,one relation among the two relations denoted by the two formulas belowis satisfied. Note that in the two formulas below, r1(t) and r2(t)indicate reception signals, and h11(t), h12(t), h21(t), and h22(t)indicate channel fluctuation values.

In the case of Example 1, Example 2 and Example 3, the followingrelationship shown in formula 89 is derived from FIG. 5.

$\begin{matrix}( {{formula}\mspace{14mu} 89} ) & \; \\\begin{matrix}{\begin{pmatrix}{r\; 1(t)} \\{r\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}^{j\; 0} & 0 \\0 & {u\; ^{j\; 0}}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}1 & 0 \\0 & u\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{s\; 1(t)} \\{{us}\; 2(t)}\end{pmatrix}}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 89} \rbrack\end{matrix}$

Also, as explained in Example 1, Example 2, and Example 3, therelationship may be as shown in formula 90 below:

$\begin{matrix}( {{formula}\mspace{14mu} 90} ) & \; \\\begin{matrix}{\begin{pmatrix}{r\; 1(t)} \\{r\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{u\; ^{j\; 0}} & 0 \\0 & ^{j\; 0}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}u & 0 \\0 & 1\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{{us}\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 90} \rbrack\end{matrix}$

The reception device performs demodulation (detection) (i.e. estimatesthe bits transmitted by the transmission device) by using therelationships described above (in the same manner as described inEmbodiment 1 and so on).

In the case of Example 4, Example 5 and Example 6, the followingrelationship shown in formula 91 is derived from FIG. 5.

$\begin{matrix}( {{formula}\mspace{14mu} 91} ) & \; \\\begin{matrix}{\begin{pmatrix}{r\; 1(t)} \\{r\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{v\; ^{j\; 0}} & 0 \\0 & {u\; ^{j\; 0}}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}v & 0 \\0 & {v \times w}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{{vs}\; 1(t)} \\{{us}\; 2(t)}\end{pmatrix}}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{{vs}\; 1(t)} \\{v \times w \times s\; 2(t)}\end{pmatrix}}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 91} \rbrack\end{matrix}$

Also, as explained in Example 3, Example 4, and Example 5, therelationship may be as shown in formula 92 below:

$\begin{matrix}( {{formula}\mspace{14mu} 92} ) & \; \\\begin{matrix}{\begin{pmatrix}{r\; 1(t)} \\{r\; 2(t)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}{z\; 1(t)} \\{z\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{u\; ^{j\; 0}} & 0 \\0 & {v\; ^{j\; 0}}\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{v \times w} & 0 \\0 & v\end{pmatrix}}\begin{pmatrix}{s\; 1(t)} \\{s\; 2(t)}\end{pmatrix}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{{us}\; 1(t)} \\{{vs}\; 2(t)}\end{pmatrix}}}} \\{= {\begin{pmatrix}{h\; 11(t)} & {h\; 12(t)} \\{h\; 21(t)} & {h\; 22(t)}\end{pmatrix}\begin{pmatrix}1 & 0 \\0 & {y(t)}\end{pmatrix}{F\begin{pmatrix}{v \times {ws}\; 1(t)} \\{{vs}\; 2(t)}\end{pmatrix}}}}\end{matrix} & \lbrack {{Math}.\mspace{14mu} 92} \rbrack\end{matrix}$

The reception device performs demodulation (detection) (i.e. estimatesthe bits transmitted by the transmission device) by using therelationships described above (in the same manner as described inEmbodiment 1 and so on).

Note that although Examples 1 through 6 show the case where the powerchanger is added to the transmission device, the power change may beperformed at the stage of mapping.

As described in Example 1, Example 2, and Example 3, and as particularlyshown in formula 89, the mapper 306B in FIG. 3 and FIG. 4 may outputu×s2(t), and the power changer may be omitted in such cases. If this isthe case, it can be said that the scheme for regularly changing thephase is applied to the signal s1(t) after the mapping and the signalu×s2(t) after the mapping, the modulated signal after precoding.

As described in Example 1, Example 2, and Example 3, and as particularlyshown in formula 90, the mapper 306A in FIG. 3 and FIG. 4 may outputu×s1(t), and the power changer may be omitted in such cases. If this isthe case, it can be said that the scheme for regularly changing thephase is applied to the signal s2(t) after the mapping and the signalu×s1(t) after the mapping, the modulated signal after precoding.

In Example 4, Example 5, and Example 6, as particularly shown in formula91, the mapper 306A in FIG. 3 and FIG. 4 may output v×s1(t), and themapper 306B may output u×s2(t), and the power changer may be omitted insuch cases. If this is the case, it can be said that the scheme forregularly changing the phase is applied to the signal v×s1(t) after themapping and the signal u×s2(t) after the mapping, the modulated signalsafter precoding.

In Example 4, Example 5, and Example 6, as particularly shown in formula92, the mapper 306A in FIG. 3 and FIG. 4 may output u×s1(t), and themapper 306B may output v×s2(t), and the power changer may be omitted insuch cases. If this is the case, it can be said that the scheme forregularly changing the phase is applied to the signal u×s1(t) after themapping and the signal v×s2(t) after the mapping, the modulated signalsafter precoding.

Note that F shown in formulas 89 through 92 denotes precoding matricesused at time t, and y(t) denotes phase changing values. The receptiondevice performs demodulation (detection) by using the relationshipsbetween r1(t), r2(t) and s1(t), s2(t) described above (in the samemanner as described in Embodiment 1 and so on). However, distortioncomponents, such as noise components, frequency offset, channelestimation error, and the likes are not considered in the formulasdescribed above. Hence, demodulation (detection) is performed with them.Regarding the values u and v that the transmission device uses forperforming the power change, the transmission device transmitsinformation about these values, or transmits information of thetransmission mode (such as the transmission scheme, the modulationscheme and the error correction scheme) to be used. The reception devicedetects the values used by the transmission device by acquiring theinformation, obtains the relationships described above, and performs thedemodulation (detection).

In the present embodiment, the switching between the phase changingvalues is performed on the modulated signal after precoding in the timedomain. However, when a multi-carrier transmission scheme such as anOFDM scheme is used, the present invention is applicable to the casewhere the switching between the phase changing values is performed onthe modulated signal after precoding in the frequency domain, asdescribed in other embodiments. If this is the case, t used in thepresent embodiment is to be replaced with f (frequency ((sub) carrier)).

Accordingly, in the case of performing the switching between the phasechanging values on the modulated signal after precoding in the timedomain, z1 (t) and z2(t) at the same time point is transmitted fromdifferent antennas by using the same (common/shared) frequency. On theother hand, in the case of performing the switching between the phasechanging values on the modulated signal after precoding in the frequencydomain, z1(f) and z2(f) at the same (common/shared) frequency istransmitted from different antennas at the same time point.

Also, even in the case of performing switching between the phasechanging values on the modulated signal after precoding in the time andfrequency domains, the present invention is applicable as described inother embodiments. The scheme pertaining to the present embodiment,which switches between the phase changing values on the modulated signalafter precoding, is not limited the scheme which switches between thephase changing values on the modulated signal after precoding asdescribed in the present Description.

Also, assume that processed baseband signals z1(i), z2(i) (where irepresents the order in terms of time or frequency (carrier)) aregenerated by regular phase change and precoding (it does not matterwhich is performed first) on baseband signals s1(i) and s2(i) for twostreams. Let the in-phase component I and the quadrature component Q ofthe processed baseband signal z1(i) be I₁(i) and Q₁(i) respectively, andlet the in-phase component I and the quadrature component Q of theprocessed baseband signal z2(i) be I₂(i) and Q₂(i) respectively. In thiscase, the baseband components may be switched, and modulated signalscorresponding to the switched baseband signal r1(i) and the switchedbaseband signal r2(i) may be transmitted from different antennas at thesame time and over the same (common/shared) frequency by transmitting amodulated signal corresponding to the switched baseband signal r1(i)from transmit antenna 1 and a modulated signal corresponding to theswitched baseband signal r2(i) from transmit antenna 2 at the same timeand over the same (common/shared) frequency. Baseband components may beswitched as follows.

-   -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i) and Q₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i) and I₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₁(i) and Q₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₁(i) and Q₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i) and I₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i) and Q₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₁(i) and I₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₁(i) and I₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i) and I₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₁(i) and Q₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r₁(i) be Q₁(i) and Q₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i) and I₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i) and Q₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i) and Q₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₁(i) and I₂(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i) and Q₁(i) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₂(i) and I₁(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₁(i) and I₂(i) respectively.

In the above description, signals in two streams are processed andin-phase components and quadrature components of the processed signalsare switched, but the present invention is not limited in this way.Signals in more than two streams may be processed, and the in-phasecomponents and quadrature components of the processed signals may beswitched.

In addition, the signals may be switched in the following manner. Forexample,

-   -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i) and Q₂(i) respectively,        and the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i) and Q₁(i) respectively.

Such switching can be achieved by the structure shown in FIG. 55.

In the above-mentioned example, switching between baseband signals atthe same time (at the same (common/shared) frequency ((sub)carrier)) hasbeen described, but the present invention is not limited to theswitching between baseband signals at the same time. As an example, thefollowing description can be made.

-   -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i+v) and Q₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be I₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i+v) and I₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be Q₁(i+v) and        Q₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be Q₁(i+v) and        Q₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i+v) and I₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be Q₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be Q₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₁(i+v) and Q₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be Q₁(i+v) and        I₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be I₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be Q₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be Q₁(i+v) and        I₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i+v) and I₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be Q₁(i+v) and        Q₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be Q₁(i+v) and        Q₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i+v) and I₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be Q₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be Q₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i+v) and Q₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be I₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be I₁(i+v) and Q₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be Q₁(i+v) and        I₂(i+w) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be I₂(i+w) and        Q₁(i+v) respectively.    -   Let the in-phase component and the quadrature component of the        switched baseband signal r2(i) be Q₂(i+w) and I₁(i+v)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r1(i) be Q₁(i+v) and        I₂(i+w) respectively.

In addition, the signals may be switched in the following manner. Forexample,

-   -   Let the in-phase component and the quadrature component of the        switched baseband signal r1(i) be I₂(i+w) and Q₂(i+w)        respectively, and the in-phase component and the quadrature        component of the switched baseband signal r2(i) be I₁(i+v) and        Q₁(i+w) respectively.

This can also be achieved by the structure shown in FIG. 55.

FIG. 55 illustrates a baseband signal switcher 5502 explaining theabove. As shown, of the two processed baseband signals z1(i) 5501_1 andz2(i) 5501_2, processed baseband signal z1(i) 5501_1 has in-phasecomponent I₁(i) and quadrature component Q₁(i), while processed basebandsignal z2(i) 5501_2 has in-phase component I₂(i) and quadraturecomponent Q₂(i). Then, after switching, switched baseband signal r1(i)5503_1 has in-phase component I_(r1)(i) and quadrature componentQ_(r1)(i), while switched baseband signal r2(i) 5503_2 has in-phasecomponent I_(r2)(i) and quadrature component Q_(r2)(i). The in-phasecomponent I_(r1)(i) and quadrature component Q_(r1)(i) of switchedbaseband signal r1(i) 5503_1 and the in-phase component Ir2(i) andquadrature component Q_(r2)(i) of switched baseband signal r2(i) 5503_2may be expressed as any of the above. Although this example describesswitching performed on baseband signals having a common time (common((sub-)carrier) frequency) and having undergone two types of signalprocessing, the same may be applied to baseband signals having undergonetwo types of signal processing but having different time (different((sub-)carrier) frequencies).

The switching may be performed while regularly changing switchingmethods.

For example,

-   -   At time 0,        for switched baseband signal r1(0), the in-phase component may        be I₁(0) while the quadrature component may be Q₁(0), and for        switched baseband signal r2(0), the in-phase component may be        I₂(0) while the quadrature component may be Q₂(0);    -   At time 1,        for switched baseband signal r1(1), the in-phase component may        be I₂(1) while the quadrature component may be Q₂(1), and for        switched baseband signal r2(1), the in-phase component may be        I_(i)(1) while the quadrature component may be Q₁(1), and so on.        In other words,    -   When time is 2k (k is an integer),        for switched baseband signal r1(2k), the in-phase component may        be I₁(2k) while the quadrature component may be Q_(i)(2k), and        for switched baseband signal r2(2k), the in-phase component may        be I₂(2k) while the quadrature component may be Q₂(2k).    -   When time is 2k+1 (k is an integer),        for switched baseband signal r1(2k+1), the in-phase component        may be I₂(2k+1) while the quadrature component may be Q₂(2k+1),        and for switched baseband signal r2(2k+1), the in-phase        component may be I₁(2k+1) while the quadrature component may be        Q_(i)(2k+1).    -   When time is 2k (k is an integer),        for switched baseband signal r1(2k), the in-phase component may        be I₂(2k) while the quadrature component may be Q₂(2k), and for        switched baseband signal r2(2k), the in-phase component may be        I₁(2k) while the quadrature component may be Q₁(2k).    -   When time is 2k+1 (k is an integer),        for switched baseband signal r1(2k+1), the in-phase component        may be I₁(2k+1) while the quadrature component may be        Q_(i)(2k+1), and for switched baseband signal r2(2k+1), the        in-phase component may be I₂(2k+1) while the quadrature        component may be Q₂(2k+1).

Similarly, the switching may be performed in the frequency domain. Inother words,

-   -   When frequency ((sub) carrier) is 2k (k is an integer),        for switched baseband signal r1(2k), the in-phase component may        be I₁(2k) while the quadrature component may be Q_(i)(2k), and        for switched baseband signal r2(2k), the in-phase component may        be I₂(2k) while the quadrature component may be Q₂(2k).    -   When frequency ((sub) carrier) is 2k+1 (k is an integer),        for switched baseband signal r1(2k+1), the in-phase component        may be I₂(2k+1) while the quadrature component may be Q₂(2k+1),        and for switched baseband signal r2(2k+1), the in-phase        component may be I₁(2k+1) while the quadrature component may be        Q_(i)(2k+1).    -   When frequency ((sub) carrier) is 2k (k is an integer),        for switched baseband signal r1(2k), the in-phase component may        be I₂(2k) while the quadrature component may be Q₂(2k), and for        switched baseband signal r2(2k), the in-phase component may be        I₁(2k) while the quadrature component may be Q₁(2k).    -   When frequency ((sub) carrier) is 2k+1 (k is an integer),        for switched baseband signal r1(2k+1), the in-phase component        may be I₁(2k+1) while the quadrature component may be        Q_(i)(2k+1), and for switched baseband signal r2(2k+1), the        in-phase component may be I₂(2k+1) while the quadrature        component may be Q₂(2k+1).

(Regarding Cyclic Q Delay)

The following describes the application of the Cyclic Q Delay mentionedthroughout the present disclosure. Non-Patent Literature 10 describesthe overall concept of Cyclic Q Delay. The following describes aspecific example of a generation method for the s1 and s2 signals whenCyclic Q Delay is used.

FIG. 102 illustrates an example of a signal point arrangement in the I-Qplane when the modulation scheme is 16-QAM. As shown, when the inputbits are b0, b1, b2, and b3, the bits take on either a value of 0000 ora value of 1111. For example, when the bits b0, b1, b2, and b3 are to beexpressed as 0000, then signal point 10201 of FIG. 102 is selected, avalue of the in-phase component based on signal point 10201 is taken asthe in-phase component of the baseband signal, and a value of thequadrature component based on signal point 10201 is taken as thequadrature component of the baseband signal. When the bits b0, b1, b2,and b3 are to be expressed as a different value, the in-phase componentand the quadrature component of the baseband signal are generatedsimilarly.

FIG. 103 illustrates a sample configuration of a signal generator forgenerating modulated signals s1(t) (where t is time) (alternatively, s1(f), where f is frequency) and s2(t) (alternatively, s2(f)) from(binary) data when the cyclic Q delay is applied.

A mapper 10302 takes data 10301 and a control signal 10306 as input, andperforms mapping in accordance with the modulation scheme of the controlsignal 10306. For example, when 16-QAM is selected as the modulationscheme, mapping is performed as illustrated in FIG. 102. The mapper thenoutputs an in-phase component 10303_A and a quadrature component 10303_Bfor the mapped baseband signal. No limitation is intended to themodulation scheme being 16-QAM, and the operations are similar for othermodulation schemes.

Here, the data at time 1 corresponding to the bits b0, b1, b2, and b3from FIG. 102 are respectively indicated as b01, b11, b21, and b31. Themapper 10302 outputs the in-phase component I1 and the quadraturecomponent Q1 for the baseband signal at time 1, according to the datab0, b1, b2, and b3 at time 1. Similarly, another mapper 10302 outputsthe in-phase component I2 and the quadrature component Q2 and so on forthe baseband signal at time 2.

A memory and signal switcher 10304 takes the in-phase component 10303_Aand the quadrature component 10303_B of the baseband signal as inputand, in accordance with a control signal 10306, stores the in-phasecomponent 10303_A and the quadrature component 10303_B of the basebandsignal, switches the signals, and outputs modulated signal s1(t)(10305_A) and modulated signal s2(t) (10305_B). The generation methodfor the modulated signals s1(t) and s2(t) is described in detail below.

As described elsewhere in the disclosure, precoding and phase changingare performed on the modulated signal s1(t) and s2(t). Here, asdescribed elsewhere, signal processing involving phase change, powerchange, signal switching, and so on may be applied at any step. Thus,modulated signals r1(t) and r2(t), respectively obtained by applying theprecoding and phase change to the modulated signals s1(t) and s2(t), aretransmitted using the same (common) frequency band at the same (common)time.

Although the above description is given with respect to the time domain,s1(t) and s2(t) may be thought of as s1(f) and s2(f) (where f is the(sub-)carrier frequency) when a multi-carrier transmission scheme suchas OFDM is employed. In contrast to the modulated signals s1(f) ands2(f), modulated signals r1(f) and r2(f) obtained using a precodingscheme in which the precoding matrix is regularly changed aretransmitted at the same (common) time (r1(f) and r2(f) being, of course)signals of the same (common/shared) frequency band). Also, as describedabove, s1(t) and s2(t) may be treated as s1(t,f) and s2(t,f).

The following describes the generation method for modulated signalss1(t) and s2(t). FIG. 104 illustrates a first example of a generationmethod for s1(t) and s2(t) when a cyclic Q delay is used.

Portion (a) of FIG. 104 indicates the in-phase component and thequadrature component of the baseband signal obtained by the mapper 10302of FIG. 103. As shown in FIG. 87A and as described with reference to themapper 10302 of FIG. 103, the mapper 10302 outputs the in-phasecomponent and the quadrature component of the baseband signal such thatin-phase component I1 and quadrature component Q1 occur at time 1,in-phase component I2 and quadrature component Q2 occur at time 2,in-phase component I3 and quadrature component Q3 occur at time 3, andso on.

Portion (b) of FIG. 104 illustrates a sample set of in-phase componentsand quadrature components for the baseband signal when signal switchingis performed by the memory and signal switcher 10304 of FIG. 103. Asshown, pairs of quadrature components are switched at each of time 1 andtime 2, time 3 and time 4, and time 5 and time 6 (i.e., time 2i+1 andtime 2i+2, i being a non-zero positive integer) such that, for example,the components at time 1 and t2 are switched.

Accordingly, given that signal switching is not performed on thein-phase component of the baseband signal, the order thereof is suchthat in-phase component I1 occurs at time 1, in-phase component I2occurs at time 2, baseband signal I3 occurs at time 3, and so on.

Then, signal switching is performed within the pairs of quadraturecomponents for the baseband signal. Thus, quadrature component Q2 occursat time 1, quadrature component Q1 occurs at time 2, quadraturecomponent Q4 occurs at time 3, quadrature component Q3 occurs at time 4,and so on.

Portion (c) of FIG. 104 indicates a sample configuration for modulatedsignals s1(t) and s2(t) before precoding, when the scheme appliedinvolves precoding and phase changing. For example, as shown in portion(c), the baseband signal generated in portion (b) is alternatelyassigned to s1(t) and to s2(t). Thus, the first slot of s1(t) takes (I1,Q2) and the first slot of s2(t) takes (I2, Q1). Likewise, the secondslot of s1(t) takes (I3, Q4) and the second slot of s2(t) takes (I4,Q3). This continues similarly.

Although FIG. 104 describes an example with reference to the timedomain, the same applies to the frequency domain (exactly as describedabove). In such cases, the descriptions pertain to s1(f) and 2(f).

Then, N-slot precoded and phase changed modulated signals r1(t) andr2(t) are obtained after applying the precoding and phase change to theN-slot modulated signals s1(t) and s2(t). This point is describedelsewhere in the present disclosure.

FIG. 105 illustrates a configuration that differs from that of FIG. 103and is used to obtain the N-slot s1(t) and s2(t) from FIG. 104. Themapper 10502 takes data and a control signal 10504 as input and, inaccordance with the modulation scheme of the control signal 10504, forexample, performs mapping in consideration of the switching from FIG.104, generates a mapped signal (i.e., in-phase components and quadraturecomponents of the baseband signal) and generates modulated signals1(t)(10503_A) and modulated signal s2(t)(10503_B) from the mappedsignal. Modulated signal (s1(t) (10503_A) is identical to modulatedsignal 10305_A from FIG. 103, and modulated signal s2(t) (10503_B) isidentical to modulated signal 10305_B from FIG. 103. This is asindicated in portion (c) of FIG. 104. Accordingly, the first slot ofmodulated signal s1(t) (10503_A) takes (I1, Q2), the first slot ofmodulated signal s2(t) (10503_B) takes (I2, Q1), the second slot ofmodulated signal s1(t) (10503_A) takes (I3, Q4), the second slot ofmodulated signal s2(t) (10503_B) takes (I4, Q3), and so on.

The generation method for the first slot (I1, Q2) of modulated signals1(t) (10503_A) and the first slot (I2, Q1) of modulated signal s2(t)(10503_B) by the mapper 10502 from FIG. 105 is described below, as asupplement.

The data 10501 indicated in FIG. 105 is made up of time 1 data b01, b11,b21, b31 and of time 2 data b02, b12, b22, b32. The mapper 10502 of FIG.105 generates I1, Q1, I2, and Q2 as described above using the data b01,b11, b21, b31 and b02, b12, b22, and b32. Thus, the mapper 10502 of FIG.105 is able to generate the modulated signals s1(t) and s2(t) from I1,Q1, I2, and Q2.

FIG. 106 illustrates a configuration that differs from those of FIGS.103 and 105 and is used to obtain the N-slot s1(t) and s2(t) from FIG.104. The mapper 10601_A takes data 10501 and a control signal 10504 asinput and, in accordance with the modulation scheme of the controlsignal 10504, for example, performs mapping in consideration of theswitching from FIG. 104, generates a mapped signal (i.e., in-phasecomponents and quadrature components of the baseband signal) andgenerates a modulated signal s1(t) (10503_A) from the mapped signal.Similarly, the mapper 10601_B takes data 10501 and a control signal10504 as input and, in accordance with the modulation scheme of thecontrol signal 10504, for example, performs mapping in consideration ofthe switching from FIG. 104, generates a mapped signal (i.e., in-phasecomponents and quadrature components of the baseband signal) andgenerates a modulated signal s2(t) (10503_B) from the mapped signal.

The data 10501 input to the mapper 10601_A and the data 10501 input tothe mapper 10601_B are, of course, identical data. Modulated signals1(t) (10503_A) is identical to modulated signal 10305_A from FIG. 103,and modulated signal s2(t) (10503_B) is identical to modulated signal10305_B from FIG. 6. This is as indicated in portion (c) of FIG. 104.

Accordingly, the first slot of modulated signal s1(t) (10503_A) takes(I1, Q2), the first slot of modulated signal s2(t) (10503_B) takes (I2,Q1), the second slot of modulated signal s1(t) (10503_A) takes (I3, Q4),the second slot of modulated signal s2(t) (10503_B) takes (I4, Q3), andso on.

The generation method for the first slot (I1, Q2) of modulated signals1(t) (10503_A) by the mapper 10601_A from FIG. 106 is described below,as a supplement. The data 10501 indicated in FIG. 106 are made up oftime 1 data b01, b11, b21, b31 and of time 2 data b02, b12, b22, b32.The mapper 10601_A of FIG. 106 generates 11 and Q2 as described aboveusing the data b01, b11, b21, b31 and b02, b12, b22, and b32. The mapper10601_A of FIG. 106 then generates modulated signal s1(t) from 11 andQ2.

The generation method for the first slot (I2, Q1) of modulated signals2(t) (10503_B) by the mapper 10601_B from FIG. 106 is described below.The data 10501 indicated in FIG. 106 are made up of time 1 data b01,b11, b21, b31 and of time 2 data b02, b12, b22, b32. The mapper 10601_Bof FIG. 106 generates 12 and Q1 as described above using the data b01,b11, b21, b31 and b02, b12, b22, and b32. Thus, the mapper 10601_B ofFIG. 106 is able to generate modulated signal s2(t) from 12 and Q1.

Next, FIG. 107 illustrates a second example that differs from thegeneration method of s1(t) and s2(t) from FIG. 104 is given for a casewhere the cyclic Q delay is used. In FIG. 107, reference signscorresponding to elements found in FIG. 104 are identical (i.e., thein-phase component and quadrature component of the baseband signal).

Portion (a) of FIG. 107 indicates the in-phase component and thequadrature component of the baseband signal obtained by the mapper 10302of FIG. 103. Portion (a) of FIG. 107 is identical to portion (a) of FIG.104. Explanations thereof are thus omitted.

Portion (b) of FIG. 107 illustrates the configuration of the in-phasecomponent and the quadrature component of the baseband signals s1(t) ands2(t) prior to signal switching. As shown, the baseband signal isallocated to s1(t) at times 2i+1, and allocated to s2(t) at times 2i+2(i being a non-zero positive integer).

Portion (c) of FIG. 107 illustrates a sample set of in-phase componentsand quadrature components for the baseband signal when signal switchingis performed by the memory and signal switcher 10304 of FIG. 103. Themain point of portion (c) of FIG. 107 (and point of difference fromportion (c) of FIG. 104) is that signal switching occurs within s1(t) aswell as s2(t).

Accordingly, in contrast to portion (b) of FIG. 107, Q1 and Q3 of s1(t)are switched in portion (c) of FIG. 107, as are Q5 and Q7. Also, incontrast to portion (b) of FIG. 107, Q2 and Q4 of s2(t) are switched inportion (c) of FIG. 107, as are Q6 and Q8.

Thus, the first slot of s1(t) has an in-phase component I1 and aquadrature component Q3, and the first slot of s2(t) has an in-phasecomponent I2 and a quadrature component Q4. Also, the second slot ofs1(t) has an in-phase component I3 and a quadrature component Q1, andthe second slot of s2(t) has an in-phase component I4 and a quadraturecomponent Q4. The third and fourth slots are as indicated in portion (c)of FIG. 107, and subsequent slots are similar.

Then, N-slot precoded and phase changed modulated signals r1(t) andr2(t) are obtained after applying the precoding and phase change to theN-slot modulated signals s1(t) and s2(t). This point is describedelsewhere in the present disclosure.

FIG. 108 illustrates a configuration that differs from that of FIG. 103and is used to obtain the N-slot s1(t) and s2(t) from FIG. 107. Themapper 10502 takes data 10501 and a control signal 10504 as input and,in accordance with the modulation scheme of the control signal 10504,for example, performs mapping in consideration of the switching fromFIG. 107, generates a mapped signal (i.e., in-phase components andquadrature components of the baseband signal) and generates modulatedsignal s1(t)(10503_A) and modulated signal s2(t)(10503_B) from themapped signal. Modulated signal s1(t) (10503_A) is identical tomodulated signal 10305_A from FIG. 103, and modulated signal s2(t)(10503_B) is identical to modulated signal 10305_B from FIG. 6. This isas indicated in portion (c) of FIG. 107. Accordingly, the first slot ofmodulated signal s1(t) (10503_A) takes (I1, Q3), the first slot ofmodulated signal s2(t) (10503_B) takes (I2, Q4), the second slot ofmodulated signal s1(t) (10503_A) takes (I3, Q1), the second slot ofmodulated signal s2(t) (10503_B) takes (I4, Q2), and so on.

The generation method for the first slot (I1, Q3) of modulated signals1(t) (10503_A), the first slot (I2, Q4) of modulated signal s2(t)(10503_B), the second slot (I3, Q1) of modulated signal s1(t) (10503_A),and the second slot (I4, Q2) of modulated signal s2(t) (10503_B) by themapper 10502 from FIG. 108 is described below, as a supplement.

The data 10501 indicated in FIG. 108 are made up of time 1 data b01,b11, b21, b31, time 2 data b02, b12, b22, b32, time 3 data b03, b13,b23, b33, and time 4 data b04, b14, b24, b34. The mapper 10502 of FIG.108 generates the aforementioned I1, Q1, I2, Q2, I3, Q3, I4, and Q4 fromthe data b01, b11, b21, b31, b02, b12, b22, b32, b03, b13, b23, b33,b04. b14, b24, b34. Thus, the mapper 10502 of FIG. 108 is able togenerate the modulated signals s1(t) and s2(t) from I1, Q1, I2, Q2, I3,Q3, I4, and Q4.

FIG. 102 illustrates a configuration that differs from those of FIGS.103 and 108 and is used to obtain the N-slot s1(t) and s2(t) from FIG.107. A distributor 10201 takes data 10501 and the control signal 10504as input, distributes the data in accordance with the control signal10504, and outputs first data 10202_A and second data 10202_B. Themapper 10601_A takes the first data 10202_A and the control signal 10504as input and, in accordance with the modulation scheme of the controlsignal 10504, for example, performs mapping in consideration of theswitching from FIG. 107, generates a mapped signal (i.e., in-phasecomponents and quadrature components of the baseband signal) andgenerates a modulated signal s1(t)(10503_A) from the mapped signal.Similarly, the mapper 10601_B takes second data 10202_B and the controlsignal 10504 as input and, in accordance with the modulation scheme ofthe control signal 10504, for example, performs mapping in considerationof the switching from FIG. 107, generates a mapped signal (i.e.,in-phase components and quadrature components of the baseband signal)and generates a modulated signal s2(t) (10503_B) from the mapped signal.

Accordingly, the first slot of modulated signal s1(t) (10503_A) takes(I1, Q3), the first slot of modulated signal s2(t) (10503_B) takes (I2,Q4), the second slot of modulated signal s1(t) (10503_A) takes (I3, Q1),the second slot of modulated signal s2(t) (10503_B) takes (I4, Q2), andso on.

The generation method for the first slot (I1, Q3) of modulated signals1(t) (10503_A) and the first slot (I3, Q1) of modulated signal s2(t)(10503_B) by the mapper 10601_A from FIG. 109 is described below, as asupplement. The data 10501 indicated in FIG. 109 are made up of time 1data b01, b11, b21, b31, time 2 data b02, b12, b22, b32, time 3 datab03, b13, b23, b33, and time 4 data b04, b14, b24, b34. The distributor10901 outputs the time 1 data b01, b11, b21, b31 and the time 3 datab03, b13, b23, b33, as the first data 10902_A, and outputs the time 2data b02, b12, b22, b32 and the time 4 data b04, b14, b24, b34 as thesecond data 10902_B The mapper 10601_A of FIG. 109 generates the firstslot as (I1, Q3) and the second slot as (I3, Q1) from the data b01, b11,b21, b31, b03, b13, b23, b33. The third slot and subsequent slots aregenerated similarly.

The generation method for the first slot (I2, Q4) of modulated signals2(t) (10503_B) and the second slot (I4, Q2) by the mapper 10601_B fromFIG. 109 is described below. The mapper 10601_B from FIG. 109 generatesthe first slot as (I2, Q4) and the second slot as (I4, Q2) from the time2 data b02, b12, b22, b32 and the time 4 data b04, b14, b24, b34. Thethird slot and subsequent slots are generated similarly.

Although two methods using cyclic Q delay are described above, when thesignals are switched among slot pairs as per FIG. 104, the demodulator(detector) of the reception device is able to constrain the quantity ofcandidate signal points. This has the merit of reducing the scope ofcalculation (circuit scope). Also, when the signals are switched withins1(t) and s2(t), as per FIG. 107, the demodulator (detector) of thereception device encounters a large quantity of candidate signal points.However, time diversity gain (or frequency diversity gain when switchingis performed with respect to the frequency domain) is available, whichas the merit of enabling further improvements to the data receptionquality.

Although the above description uses examples of a 16-QAM modulationscheme, no limitation is intended. The same applies to other modulationschemes, such as QPSK, 8-QAM, 32-QAM, 64-QAM, 128-QAM, 256-QAM and soon.

Also, the cyclic Q delay method is not limited to the two schemes givenabove. For example, either of the two schemes given above may involveswitching either of the quadrature component or the in-phase componentof the baseband signal. Also, while the above describes switchingperformed at two times (e.g., switching the quadrature components of thebaseband signal at times 1 and 2), the in-phase components and (or) thequadrature components of the baseband signal may also be switched at aplurality of times. Accordingly, when the in-phase components andquadrature components of the baseband signal are generated and cyclic Qdelay is performed as in FIG. 104, then the in-phase component of thebaseband signal after cyclic Q delay at time i is Ii, and the quadraturecomponent of the baseband signal after cyclic Q delay at time i is Qj(where i≠j). Alternatively, the in-phase component of the basebandsignal after cyclic Q delay at time i is Ij, and the quadraturecomponent of the baseband signal after cyclic Q delay at time i is Qi(where i≠j). Alternatively, the in-phase component of the basebandsignal after cyclic Q delay at time i is Ij, and the quadraturecomponent of the baseband signal after cyclic Q delay at time i is Qk(where i≠j, i≠k, j≠k).

The precoding and phase change are then applied to the modulated signalss1(t) (or s1 (f), or s1 (t,f)) and s2(t) (or s2(f) or s2(t,f)) obtainedby applying the above-described cyclic Q delay. (Here, as describedelsewhere, signal processing involving phase change, power change,signal switching, and so on may be applied at any step.) Here, theprecoding and phase changing application method used on the modulatedsignal obtained with the cyclic Q delay may be any of the precoding andphase changing methods described in the present disclosure.

INDUSTRIAL APPLICABILITY

The present invention is widely applicable to wireless systems thattransmit different modulated signals from a plurality of antennas, suchas an OFDM-MIMO system. Also, the present invention is also applicablein a wired system having multiple connections (e.g., a power linecommunication system, a fibre-optic system, a digital subscriber linesystem, and so on) when MIMO transmission is used, and the modulatedsignals described in the present document are applied. The modulatedsignals may also be transmitted from a plurality of transmissionlocations.

REFERENCE SIGNS LIST

-   -   302A, 302B Encoders    -   304A, 304B Interleavers    -   306A, 306B Mappers    -   314 Signal processing scheme information generator    -   308A, 308B Weighting compositors    -   310A, 310B Wireless units    -   312A, 312B Antennas    -   317A, 317B Phase changers    -   402 Encoder    -   404 Distributor    -   504#1, 504#2 Transmit antennas    -   505#1, 505#2 Receive antennas    -   600 Weighting unit    -   701_X, 701_Y Antennas    -   703_X, 703_Y Wireless units    -   705_1 Channel fluctuation estimator    -   705_2 Channel fluctuation estimator    -   707_1 Channel fluctuation estimator    -   707_2 Channel fluctuation estimator    -   709 Control information decoder    -   711 Signal processor    -   803 Inner MIMO detector    -   805A, 805B Log-likelihood calculators    -   807A, 807B Deinterleavers    -   809A, 809B Log-likelihood ratio calculator    -   811A, 811B Soft-in/soft-out decoders    -   813A, 813B Interleavers    -   815 Memory    -   819 Coefficient generator    -   901 Soft-in/soft-out decoder    -   903 Distributor    -   1201A, 1201B OFDM-related processors    -   1302A, 1302A Serial-to-parallel converters    -   1304A, 1304B Reorderers    -   1306A, 1306B Inverse Fast Fourier Transform units    -   1308A, 1308B Wireless units

1. A transmission signal generating method comprising: applyingprecoding to a first modulated signal s1 and a second modulated signals2 to generate a first precoded signal z′1 and a second precoded signalz′2, the first modulated signal s1 having been modulated by a firstmodulation scheme at a modulation level denoted by a, the secondmodulated signal s2 having been modulated by a second modulation schemeat a modulation level denoted by b, and a and b being integerssatisfying a<b; performing a phase change on at least one of the firstprecoded signal z′1 and the second precoded signal z′2 to generate afirst transmission signal z1 and a second transmission signal z2; andoutputting the first transmission signal z1 and the second transmissionsignal z2 respectively to be transmitting from a first antenna and asecond antenna at the same time at the same frequency, the precodingbeing represented by a precoding matrix$F = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j\; 0} & {\alpha \times ^{j\; o}} \\{\alpha \times ^{j\; 0}} & ^{j\; \pi}\end{pmatrix}}$ where α=0, a phase change scheme for the phase changebeing changed regularly, and the transmission method further comprising:performing a power change involving multiplication by a weighting factoru_(a) and multiplication by a weighting factor u_(b), the weightingfactor u_(a) being used for the generation of the first transmissionsignal z1 from the first modulated signal s1, the weighting factor u_(b)being used for the generation of the second transmission signal z2 fromthe second modulated signal s2, and the weighting factor u_(a) and theweighting factor u_(b) satisfying u_(a)<u_(b).
 2. A transmission signalgenerating apparatus comprising: a weighting unit applying precoding toa first modulated signal s1 and a second modulated signal s2 to generatea first precoded signal z′1 and a second precoded signal z′2, a phasechanger performing a phase change on at least one of the first precodedsignal z′1 and the second precoded signal z′2 to generate a firsttransmission signal z1 and a second transmission signal z2; and a outputunit transmitting the first transmission signal z1 and the secondtransmission signal z2 respectively to be transmitting from a firstantenna and a second antenna at the same time at the same frequency, thefirst modulated signal s1 having been modulated by a first modulationscheme at a modulation level denoted by a, the second modulated signals2 having been modulated by a second modulation scheme at a modulationlevel denoted by b, and a and b being integers satisfying a<b, theprecoding being represented by a precoding matrix$F = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j\; 0} & {\alpha \times ^{j\; o}} \\{\alpha \times ^{j\; 0}} & ^{j\; \pi}\end{pmatrix}}$ where α=0, a phase change scheme for the phase changebeing changed regularly, and the transmission apparatus furthercomprising: a power changer performing a power change involvingmultiplication by a weighting factor u_(a) and multiplication by aweighting factor u_(b), the weighting factor u_(a) being used for thegeneration of the first transmission signal z1 from the first modulatedsignal s1, the weighting factor u_(b) being used for the generation ofthe second transmission signal z2 from the second modulated signal s2,and the weighting factor u_(a) and the weighting factor u_(b) satisfyingu_(a)<u_(b).
 3. A reception signal generating method comprising:inputting a reception signal obtained by receiving a first transmissionsignal z1 and a second transmission signal z2 respectively transmittedfrom a first antenna and a second antenna at the same time at the samefrequency, the first transmission signal z1 and the second transmissionsignal z2 having been generated by a predetermined generation process;and obtaining reception data by applying a demodulation processcorresponding to the predetermined generation process to the receptionsignal, the predetermined generation process including: applyingprecoding to a first modulated signal s1 and a second modulated signals2 to generate a first precoded signal z′1 and a second precoded signalz′2; and performing a phase change on at least one of the first precodedsignal z′1 and the second precoded signal z′2 to generate the firsttransmission signal z1 and the second transmission signal z2, the firstmodulated signal s1 having been modulated by a first modulation schemeat a modulation level denoted by a, the second modulated signal s2having been modulated by a second modulation scheme at a modulationlevel denoted by b, a and b being integers satisfying a<b, the precodingbeing represented by a precoding matrix$F = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j\; 0} & {\alpha \times ^{j\; o}} \\{\alpha \times ^{j\; 0}} & ^{j\; \pi}\end{pmatrix}}$ where α=0, a phase change scheme for the phase changebeing changed regularly, and the predetermined generation processfurther including: performing a power change involving multiplication bya weighting factor u_(a) and multiplication by a weighting factor u_(b),the weighting factor u_(a) being used for the generation of the firsttransmission signal z1 from the first modulated signal s1, the weightingfactor u_(b) being used for the generation of the second transmissionsignal z2 from the second modulated signal s2, and the weighting factoru_(a) and the weighting factor u_(b) satisfying u_(a)<u_(b).
 4. Areception signal generating apparatus comprising: an inputting unitacquiring a reception signal obtained by receiving a first transmissionsignal z1 and a second transmission signal z2 respectively transmittedfrom a first antenna and a second antenna at the same time at the samefrequency, the first transmission signal z1 and the second transmissionsignal z2 having been generated by a predetermined generation process;and a demodulator obtaining reception data by applying a demodulationprocess corresponding to the predetermined generation process to thereception signal, the predetermined generation process including:applying precoding to a first modulated signal s1 and a second modulatedsignal s2 to generate a first precoded signal z′1 and a second precodedsignal z′2; and performing a phase change on at least one of the firstprecoded signal z′1 and the second precoded signal z′2 to generate thefirst transmission signal z1 and the second transmission signal z2, thefirst modulated signal s1 having been modulated by a first modulationscheme at a modulation level denoted by a, the second modulated signals2 having been modulated by a second modulation scheme at a modulationlevel denoted by b, a and b being integers satisfying a<b, the precodingbeing represented by a precoding matrix$F = {\frac{1}{\sqrt{\alpha^{2} + 1}}\begin{pmatrix}^{j\; 0} & {\alpha \times ^{j\; o}} \\{\alpha \times ^{j\; 0}} & ^{j\; \pi}\end{pmatrix}}$ where α=0, a phase change scheme for the phase changebeing changed regularly, and the predetermined generation processfurther including: performing a power change involving multiplication bya weighting factor u_(a) and multiplication by a weighting factor u_(b),the weighting factor u_(a) being used for the generation of the firsttransmission signal z1 from the first modulated signal s1, the weightingfactor u_(b) being used for the generation of the second transmissionsignal z2 from the second modulated signal s2, and the weighting factoru_(a) and the weighting factor u_(b) satisfying u_(a)<u_(b).